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LAMP MySQL PHP

Aztecsoft php web developer interview questions and answers

1) how to increase the web page performance ?
1) Use lightweight templates
2) Put Stylesheets at the Top
3) Put Scripts at the Bottom
4) Avoid CSS Expressions like As an example, the background color could be set to alternate every hour using CSS expressions.
background-color: expression( (new Date()).getHours()%2 ? “#B8D4FF” : “#F08A00” );
5) Make JavaScript and CSS External
6) Minify JavaScript and CSS : Minification is the practice of removing unnecessary characters from code to reduce its size thereby improving load times.
7) Remove Duplicate Scripts
8) Choose over @import
9) Don’t Scale Images in HTML
10) Make favicon.ico Small and Cacheable
11) use Ajax, JSON, Jquery for fastening results
 
2) $test=array( 0=>’one’ , 2=> ‘two’ , ‘3 ‘=>’three’ , ‘3a’=>5, ‘myindex’); print_r($test); what will be the output? 
Array ( [0] => one [2] => two [3 ] => three [3a] => 5 [3] => myindex )
3) what is output of this mysql function select substring_index(‘abc@123.com’,”@”,-1); 
Ans:  123.com   explanation is below
SUBSTRING_INDEX(str,delim,count)

Returns the substring from string str before count occurrences of the delimiter delim. If count is positive, everything to the left of the final delimiter (counting from the left) is returned. If count is negative, everything to the right of the final delimiter (counting from the right) is returned. SUBSTRING_INDEX() performs a case-sensitive match when searching for delim.

mysql> SELECT SUBSTRING_INDEX('www.mysql.com', '.', 2);
        -> 'www.mysql'
mysql> SELECT SUBSTRING_INDEX('www.mysql.com', '.', -2);
        -> 'mysql.com'

This function is multi-byte safe.
 
4) An employee table having columns  id {employee id} , name {employee name},  m_id {manager id }  , write a query to select employee and their manager names  ? 
 

Main table    
id name m_id
1 John 2
2 Greek Tor 1
3 Alex John 1
4 Mike tour 1
5 Brain J 3
6 Ronald 3
7 Kin 4
8 Herod 3
9 Alen 2
10 Ronne 1

Ans:  INNER join SQL command is mostly used to join one table to it self. The biggest advantage of doing this is to get linking information from the same table. We will try to understand this with an example. The best example of INNER join will be employee table where we will keep the employee and its manager as a single record. This way by linking to the table it self we will generate a report displaying it as two linked tables. Each record will have one additional field storing the data of the manager by keeping the employee ID and we will use M_ID ( manager ID ) to link with main employee ID. This way we will link two virtual tables generated from one main table. 
let us use inner join to create one report on who is the manager of which employee. Check this SQL 
SELECT t1.id, t1.name as emp_name, t2.name as manager FROM emp as t1 INNER JOIN emp as t2 on t2.id = t1.m_id

id emp_name manager
1 John Greek Tor
2 Greek Tor John
3 Alex John John
4 Mike tour John
5 Brain J Alex John
6 Ronald Alex John
7 Kin Mike tour
8 Herod Alex John
9 Alen Greek Tor
10 Ronne John

for more :  To generate only the manager table used this SQL
SELECT t1.id,t1.name as emp_name from emp as t1 INNER JOIN emp as t2 on t1.id=t2.m_id 
Managers Table
 

 
id emp_name
2 Greek Tor
1 John
1 John
1 John
3 Alex John
3 Alex John
4 Mike tour
3 Alex John
2 Greek Tor
1 John

 
To generate only the employee table  used this SQL
SELECT t1.id,t1.name as emp_name from emp as t1 INNER JOIN emp as t2 on t2.id=t1.m_id 

   
id emp_name
1 John
2 Greek Tor
3 Alex John
4 Mike tour
5 Brain J
6 Ronald
7 Kin
8 Herod
9 Alen
10 Ronne

 
use below dump for your reference 
CREATE TABLE `emp` (
`id` int(4) NOT NULL auto_increment,
`name` varchar(25) NOT NULL default ”,
`m_id` int(4) NOT NULL default ‘0’,
UNIQUE KEY `id` (`id`)
) ENGINE=MyISAM AUTO_INCREMENT=11 DEFAULT CHARSET=latin1 AUTO_INCREMENT=11 ;
— 
— Dumping data for table `emp`
— 
INSERT INTO `emp` VALUES (1, ‘John’, 2);
INSERT INTO `emp` VALUES (2, ‘Greek Tor’, 1);
INSERT INTO `emp` VALUES (3, ‘Alex John’, 1);
INSERT INTO `emp` VALUES (4, ‘Mike tour’, 1);
INSERT INTO `emp` VALUES (5, ‘Brain J’, 3);
INSERT INTO `emp` VALUES (6, ‘Ronald’, 3);
INSERT INTO `emp` VALUES (7, ‘Kin’, 4);
INSERT INTO `emp` VALUES (8, ‘Herod’, 3);
INSERT INTO `emp` VALUES (9, ‘Alen’, 2);
INSERT INTO `emp` VALUES (10, ‘Ronne’, 1);


5) write code to read the following file content “rag.txt”  and replace postgre SQL to MySQL and output the content ?
The postgre SQL database has become the world’s most popular open source database because of its consistent fast performance, high reliability and ease of use. postgre SQL used on every continent — Yes, even Antarctica! — by individual Web developers as well as many of the world’s largest and fastest-growing organizations to save time and money powering their high-volume Web sites, business-critical systems and packaged software by postgre SQL.
Ans:
 $str = file_get_contents(‘rag.txt’);
$str = str_replace(‘postgre SQL’ ,’MySQL’, $str);
echo $str;
 
6) how we can destroy session cookie?
Ans: we can use session_destroy() or  to destroy particular cookie set it to past time using  setcookie () function like  setcookie (“TestCookie”“”time() – 3600);
7) True or False 
a) session_destroy()  : destroys all of the data from session   TRUE
b) session_unset() : frees all session variable  TRUE

c) unset($_SESSION) deletes all session data   FALSE    “Do NOT unset the whole $_SESSION with unset($_SESSION) as this will disable the registering of session variables through the $_SESSION superglobal.”  

8) $array = array( “hi”, “Hello World” , “what”, “Good Morning”);  write code to output the array contents havng more than one word ?
Ans: 
    

<? $array = array( “hi”, “Hello World” , “what”, “Good Morning”); 
$count = sizeof($array);
$i =0;
while ($i < $count )
{
echo “<br> ***********<br>”;
$exp = explode ( ” ” ,$array[$i] );
if (count($exp) > 1)
echo $array[$i] .” is having more than  one word in “. $i.” position of array  <br>”;
$i++;
}
?>
9) what is the output of the below code 
$sec_array = array(“red”, “green”, “blue”,”yellow”);
array_splice( $sec_array , 1, -1);
print_r($sec_array );   ? 

 

Ans: Array ( [0] => red [1] => yellow )
10) how we can get the second value from the last in an array ?
Ans: 
example  <? 
$check = array ( “rag”, “shara”, “sharag”, “man”,”woman”,”child”, “human”);
echo $check[count($check)-2];
?>

11)  What is the maximum length of a URL?
Microsoft states that the maximum length of a URL in Internet Explorer is 2,083 characters, with no more than 2,048 characters in the path portion of the URL
Firefox, Safari , Opera  supports more than 100,000 characters.  but some times server like Apache, IIS may not support these longer URL’s. so better to keep it short URL.


Categories
PHP

XML Interview Questions and Answers

What is XML?
The Extensible Markup Language (XML) is a general-purpose specification for creating custom markup languages.[1] It is classified as an extensible language, because it allows the user to define the mark-up elements. XML’s purpose is to aid information systems in sharing structured data.
What is the version information in XML?
The root element can be preceded by an optional XML declaration element stating what XML version is in use (normally 1.0); it might also contain character encoding and external dependencies information.
What is ROOT element in XML?
XML documents must contain one element that is the parent of all other elements. This element is called the root element.
If XML does not have closing tag will it work?
All XML Elements Must Have a Closing Tag otherwise it will produce error while accessing or parsing.
Is XML case sensitive?
yes it is. XML tags are case sensitive. With XML, the tag is different from the tag .
Opening and closing tags must be written with the same case.
What’s the difference between XML and HTML?
On the surface, XML and HTML look similar. Both use tags (such as or ) and attributes (such as align=”left” or type=”personal”) to add information to the content. In fact, a carefully prepared HTML document can double as an XML document. The difference is that HTML is a well-defined set of elements and attributes. For example, the following is a well-formed XML document, but because it only uses tags that are defined in HTML, it’s also an HTML document:
Message of the Day

There is no message of the day.

Try back tomorrow.

On the other hand, HTML has somewhat looser rules than XML, so some HTML documents are not well-formed XML documents.
Is XML meant to replace HTML?
xml is a portable document structure, which is not really for presentation. XSL or CSS may replace html, but really xml is meant to be a storage medium. It is like asking if databases will replace html.
The one aspect that makes this whole thing blurry is that html and now Xhtml is a subset of xml. It is just used to make documents render in browsers.
Can you explain why your project needed XML?
1. If we having huge datas to be transferred instead of sending all those datas as dataset you can opt xml.
2. XML is easy to parse and it enables a faster accessing of datas.
3. Case sensitiveness is an additional advantage in validating the authentication for the user.
4. XML can be passed irrespective of OS, port and protocol.
What is DTD (Document Type definition)?
A Document Type Definition (DTD) defines the legal building blocks of an XML document. It defines the document structure with a list of legal elements and attributes.
A DTD can be declared inline inside an XML document, or as an external reference
Although XML allows you to invent as many different elements and attributes as you need, these elements and attributes, as well as their contents and the documents that contain them, must all follow certain rules in order to be well-formed. If a document is not well-formed, any attempts to read it or render it will fail.
What is a valid XML?
XML that meets the constraints defined by its Document Type Declaration.
What is CDATA section in XML?
CDATA Sections are used to escape blocks of text containing characters which would otherwise be recognized as markup. All tags and entity references are ignored by an XML processor that treats them just like any character data. CDATA blocks have been provided as a convenience measure when you want to include large blocks of special characters as character data, but you do not want to have to use entity references all the time
What is XSL?
Extensible Style Language is a style sheet language aimed at activities such as rearranging the document that are not supported by CSS, though XSL and CSS share the same underlying concepts. XSL can be used to style XML documents u sing sets of rules and definitions of actions to be applied. XSL is a specification from the W3C.
What is Element and attributes in XML?
The basic building blocks of XML Schemas are elements and attributes. Data types define the valid content that elements and attributes contain. When you create XML Schemas, you define the individual elements and attributes and assign valid types to them. Elements describe data, whereas attributes are like properties of an element, in that they provide further definition about the element the way that properties describe characteristics of objects and classes.
An element describes the data that it contains. Elements can also contain other elements and attributes.
An attribute is a named simple-type definition that cannot contain other elements. Attributes can also be assigned an optional default value and they must appear at the bottom of complex-type definitions. Additionally, if multiple attributes are declared, they may occur in any order.
What are the standard ways of parsing XML document?
DOM and SAX parsers are the standard ways for parsing XML document.
In What scenarios will you use a DOM parser and SAX parser?
In some scenarios, SAX is easily the better choice for quick, less-intensive parsing and processing. In others, the DOM provides an easy-to-use, clean interface to data in a desirable format. You, the developer, must always analyze your application and its purpose to make the correct decision as to which method to use, or how to use both in concert.
What is XSLT?
Extensible Stylesheet Language Transformations. A programming language specialized for the transformation of XML documents.
Define XPATH?
A query language used to identify a set of nodes within a XML document. Originally defined to be used with XSLT, it is also used by XPointer and a simple subset is used in the xs:key, xs:keyref, and xs:unique W3C XML Schema elements. The XQuery specification will be a superset of the second version of XPath. This version will use type information provided by W3C XML Schema
What is an XMLReader Class?
Represents a reader that provides fast, non-cached, forward-only access to XML data.
XmlReader provides forward-only, read-only access to a stream of XML data. The XmlReader class conforms to the W3C Extensible Markup Language (XML) 1.0 and the Namespaces in XML recommendations.
What is XMLTextReader?
The XmlTextReader class requires fast access to XML data. It does not require reading the entire document into memory via the Document Object Model (DOM). The class is derived from the XmlReader class and implements all the methods defined in the XmlReader class. The following are the functions of the XmlTextReader class:
* It enforces rules of a well-formed XML document.
* It does not provide any data validation in a document.
* It checks the Document Type Definition (DTD) and DocumentType nodes for their well-formed structure, but does not validate these nodes by using the DTD.
How do we access attributes using “XmlReader”?
The XmlReader class provides various methods and properties for reading attributes. Attributes are most commonly found on elements. However, they are also allowed on XML declaration and document type nodes.
When positioned on an element node, the MoveToAttribute methods enable you to go through the attribute list of the element. After MoveToAttribute has been called, the node properties—such as Name, NamespaceURI, Prefix, and so on—reflect the properties of that attribute, and not the containing element it belongs to.
What does XmlValidatingReader class do?
Represents a reader that provides document type definition (DTD), XML-Data Reduced (XDR) schema, and XML Schema definition language (XSD) validation.
XmlValidatingReader implements the XmlReader class and provides support for data validation. Use the Schemas property to have the reader validate by using schema files that are cached in an XmlSchemaCollection. The ValidationType property specifies what type of validation the reader should perform. Setting the property to ValidationType.None creates a non-validating reader.

Categories
PHP

AJAX Interview Questions and Answers

What’s AJAX?
AJAX (Asynchronous JavaScript and XML) is a newly coined term for two powerful browser features that have been around for years, but were overlooked by many web developers until recently when applications such as Gmail, Google Suggest, and Google Maps hit the streets.
Asynchronous JavaScript and XML, or Ajax (pronounced “Aye-Jacks”), is a web development technique for creating interactive web applications using a combination of XHTML (or HTML) and CSS for marking up and styling information. (XML is commonly used, although any format will work, including preformatted HTML, plain text, JSON and even EBML).
The Document Object Model manipulated through JavaScript to dynamically display and interact with the information presented
The XMLHttpRequest object to exchange data asynchronously with the web server. In some Ajax frameworks and in some situations, an IFrame object is used instead of the XMLHttpRequest object to exchange data with the web server.
Like DHTML, LAMP, or SPA, Ajax is not a technology in itself, but a term that refers to the use of a group of technologies together. In fact, derivative/composite technologies based substantially upon Ajax, such as AFLAX, are already appearing.
Ajax applications are mostly executed on the user’s computer; they can perform a number of tasks without their performance being limited by the network. This permits the development of interactive applications, in particular reactive and rich graphic user interfaces.
Ajax applications target a well-documented platform, implemented by all major browsers on most existing platforms. While it is uncertain that this compatibility will resist the advent of the next generations of browsers (in particular, Firefox), at the moment, Ajax applications are effectively cross-platform.
While the Ajax platform is more restricted than the Java platform, current Ajax applications effectively fill part of the one-time niche of Java applets: extending the browser with portable, lightweight mini-applications.
Ajax isn’t a technology. It’s really several technologies, each flourishing in its own right, coming together in powerful new ways. Ajax incorporates:
* standards-based presentation using XHTML and CSS;
* dynamic display and interaction using the Document Object Model;
* data interchange and manipulation using XML and XSLT; * asynchronous data retrieval using XMLHttpRequest;
* and JavaScript binding everything together.
Who’s Using Ajax ?
Google is making a huge investment in developing the Ajax approach. All of the major products Google has introduced over the last year ? Orkut, Gmail, the latest beta version of Google Groups, Google Suggest, and Google Maps ? are Ajax applications. (For more on the technical nuts and bolts of these Ajax implementations, check out these excellent analyses of Gmail, Google Suggest, and Google Maps.) Others are following suit: many of the features that people love in Flickr depend on Ajax, and Amazon?s A9.com search engine applies similar techniques.
These projects demonstrate that Ajax is not only technically sound, but also practical for real-world applications. This isn?t another technology that only works in a laboratory. And Ajax applications can be any size, from the very simple, single-function Google Suggest to the very complex and sophisticated Google Maps.
Who’s Using Ajax ?
Google is making a huge investment in developing the Ajax approach. All of the major products Google has introduced over the last year ? Orkut, Gmail, the latest beta version of Google Groups, Google Suggest, and Google Maps ? are Ajax applications. (For more on the technical nuts and bolts of these Ajax implementations, check out these excellent analyses of Gmail, Google Suggest, and Google Maps.) Others are following suit: many of the features that people love in Flickr depend on Ajax, and Amazon?s A9.com search engine applies similar techniques.
These projects demonstrate that Ajax is not only technically sound, but also practical for real-world applications. This isn?t another technology that only works in a laboratory. And Ajax applications can be any size, from the very simple, single-function Google Suggest to the very complex and sophisticated Google Maps.
At Adaptive Path, we?ve been doing our own work with Ajax over the last several months, and we?re realizing we?ve only scratched the surface of the rich interaction and responsiveness that Ajax applications can provide. Ajax is an important development for Web applications, and its importance is only going to grow. And because there are so many developers out there who already know how to use these technologies, we expect to see many more organizations following Google?s lead in reaping the competitive advantage Ajax provides.
Moving Forward
The biggest challenges in creating Ajax applications are not technical. The core Ajax technologies are mature, stable, and well understood. Instead, the challenges are for the designers of these applications: to forget what we think we know about the limitations of the Web, and begin to imagine a wider, richer range of possibilities
Should I consider AJAX?
AJAX definitely has the buzz right now, but it might not be the right thing for you. AJAX is limited to the latest browsers, exposes browser compatibility issues, and requires new skill-sets for many. There is a good blog entry by Alex Bosworth on AJAX Mistakes which is a good read before you jump full force into AJAX.
On the other hand you can achieve highly interactive rich web applications that are responsive and appear really fast. While it is debatable as to whether an AJAX based application is really faster, the user feels a sense of immediacy because they are given active feedback while data is exchanged in the background. If you are an early adopter and can handle the browser compatibility issues, and are willing to learn some more skills, then AJAX is for you. It may be prudent to start off AJAX-ifying a small portion or component of your application first. We all love technology, but just remember the purpose of AJAX is to enhance your user’s experience and not hinder it.
Does AJAX work with Java?
Absolutely. Java is a great fit for AJAX! You can use Java Enterprise Edition servers to generate AJAX client pages and to serve incoming AJAX requests, manage server side state for AJAX clients, and connect AJAX clients to your enterprise resources. The JavaServer Faces component model is a great fit for defining and using AJAX components.
Won’t my server-side framework provide me with AJAX?
You may be benefiting from AJAX already. Many existing Java based frameworks already have some level of AJAX interactions and new frameworks and component libraries are being developed to provide better AJAX support. I won’t list all the Java frameworks that use AJAX here, out of fear of missing someone, but you can find a good list at www.ajaxpatterns.org/Java_Ajax_Frameworks.
If you have not chosen a framework yet it is recommended you consider using JavaServer Faces or a JavaServer Faces based framework. JavaServer Faces components can be created and used to abstract many of the details of generating JavaScript, AJAX interactions, and DHTML processing and thus enable simple AJAX used by JSF application developer and as plug-ins in JSF compatible IDE’s, such as Sun Java Studio Creator.
Where should I start?
Assuming the framework you are using does not suffice your use cases and you would like to develop your own AJAX components or functionality I suggest you start with the article Asynchronous JavaScript Technology and XML (AJAX) With Java 2 Platform, Enterprise Edition.
If you would like to see a very basic example that includes source code you can check out the tech tip Using AJAX with Java Technology. For a more complete list of AJAX resources the Blueprints AJAX home page.
Next, I would recommend spending some time investigating AJAX libraries and frameworks. If you choose to write your own AJAX clients-side script you are much better off not re-inventing the wheel.
AJAX in Action by Dave Crane and Eric Pascarello with Darren James is good resource. This book is helpful for the Java developer in that in contains an appendix for learning JavaScript for the Java developer.
Did Adaptive Path invent Ajax? Did Google? Did Adaptive Path help build Google?s Ajax applications?
Neither Adaptive Path nor Google invented Ajax. Google?s recent products are simply the highest-profile examples of Ajax applications. Adaptive Path was not involved in the development of Google?s Ajax applications, but we have been doing Ajax work for some of our other clients.
Is it possible to set session variables from javascript?
It’s not possible to set any session variables directly from javascript as it is purely a client side technology. You can use AJAX though to asyncronously…
Cannot parse XML generated by JSP I am generating an XML using JSP, when i run the JSP in IE it shows the XML as per DOM, but when i try to parse it using Javascript , the command xmldoc.documentElement…
This is working code I am using, it might help you. if (!isIE) xmldoc = req.responseXML; else { //IE does not take the responseXML as…
What do I need to know to create my own AJAX functionality?
If you plan not to reuse and existing AJAX component here are some of the things you will need to know.
Plan to learn Dynamic HTML (DHTML), the technology that is the foundation for AJAX. DHTML enables browser-base real time interaction between a user and a web page. DHTML is the combination of JavaScript, the Document Object Model (DOM) and Cascading Style Sheets (CSS).
* JavaScript – JavaScript is a loosely typed object based scripting language supported by all major browsers and essential for AJAX interactions. JavaScript in a page is called when an event in a page occurs such as a page load, a mouse click, or a key press in a form element.
* DOM – An API for accessing and manipulating structured documents. In most cases DOM represent the structure of XML and HTML documents.
* CSS – Allows you to define the presentation of a page such as fonts, colors, sizes, and positioning. CSS allow for a clear separation of the presentation from the content and may be changed programmatically by JavaScript.
Understanding the basic request/response nature of HTTP is also important. Many subtle bugs can result if you ignore the differences between the GET and OIst methods when configuring an XMLHttpRequest and HTTP response codes when processing callbacks.
JavaScript is the client-side glue, in a sense. JavaScript is used to create the XMLHttpRequest Object and trigger the asynchronous call. JavaScript is used to parse the returned content. JavaScript is used to analyze the returned data and process returned messages. JavaScript is used to inject the new content into the HTML using the DOM API and to modify the CSS.
Do I really need to learn JavaScript?
Basically yes if you plan to develop new AJAX functionality for your web application.
On the other hand, JSF components and component libraries can abstract the details of JavaScript, DOM and CSS. These components can generate the necessary artifacts to make AJAX interactions possible. Visual tools such as Java Studio Creator may also use AJAX enabled JSF components to create applications, shielding the tool developer from many of the details of
AJAX. If you plan to develop your own JSF components or wire the events of components together in a tool it is important that you have a basic understanding of JavaScript. There are client-side JavaScript libraries (discussed below) that you can call from your in page JavaScript that abstract browser differences. Object Hierarchy and Inheritance in JavaScript is a great resource for a Java developer to learn about JavaScript objects.
Do Ajax applications always deliver a better experience than traditional web applications?
Not necessarily. Ajax gives interaction designers more flexibility. However, the more power we have, the more caution we must use in exercising it. We must be careful to use Ajax to enhance the user experience of our applications, not degrade it.
What JavaScript libraries and frameworks are available?
There are many libraries/frameworks out there (and many more emerging) that will help abstract such things as all the nasty browser differences. Three good libraries are The Dojo Toolkit, Prototype, and DWR.
* The Dojo Toolkit contains APIs and widgets to support the development of rich web applications. Dojo contains an intelligent packaging system, UI effects, drag and drop APIs, widget APIs, event abstraction, client storage APIs, and AJAX interaction APIs. Dojo solves common usability issues such as support for dealing with the navigation such as the ability to detect the browser back button, the ability to support changes to the URL in the URL bar for bookmarking, and the ability to gracefully degrade when AJAX/JavaScript is not fully support on the client. Dojo is the Swiss Army Knife of JavaScript libraries. It provides the widest range of options in a single library and it does a very good job supporting new and older browsers.
* Prototype focuses on AJAX interactions including a JavaScript AJAX object that contains a few objects to do basic tasks such as make a request, update a portion of a document, insert content into a document, and update a portion of a document periodically. Prototype JavaScript library contains a set of JavaScript objects for representing AJAX requests and contains utility functions for accessing in page components and DOM manipulations. Script.aculo.us and Rico are built on top of Prototype and provide UI effects, support for drag and drop, and include common JavaScript centric widgets. If you are just looking to support AJAX interactions and a few basic tasks Prototype is great. If you are looking for UI effects Rico and Script.aculo.us are good options.
* Yahoo UI Library is a utility library and set of widgets using the APIs to support rich clients. The utility library includes support for cross-browser AJAX interactions, animation, DOM scriptging support, drag and drop, and cross browser event support. The Yahoo UI Library is well documnented and contains many examples.
* DWR (Dynamic Web Remoting) is a client-side and server-side framework that focuses on allowing a developer to do RPC calls from client-side JavaScript to plain old Java objects in a Java Enterprise Edition web container. On the server side DWR uses a Servlet to interact with the Java objects and returns object representations of the Java objects or XML documents. DWR will be easy to get up and running and plays well with other Java technologies. If you are looking for a client-side and server-side framework that integrates well use DWR.
* Google Web Toolkit (GWT) is client/server framework provided by Google that allows a developer to write an AJAX application in pure Java. The GWT takes care of the details of generating all the client-side code using a Java-to-JavaScript compiler. One of the key benefits of the GWT Software Developer Kit (SDK) is that it allows you to debug your applications in what is known as GWT hosted mode using an embedded browser (IE on Windows and Mozilla/Gecko on Linux) that is tied to the toolkit. In GWT hosted mode you setup through the code and debug it as it is running on both the client and server. The GWT contains a default set of widgets and widget containers. An application is built by coding a set of widgets and containers together much like would be done in a Swing application. The GWT Software Developer Kit (SDK) is limited to Linux and Windows XP/2000 though the web applications it generates are compatible with the latest generation of the mainstream browsers.
There are many new and emerging libraries for JavaScript and this list only reviews some of the more common libraries. When making a choice choose the library which suites your needs the best. While it might be better to choose one, there is nothing stopping you from using more than one framework. For a more extensive list of client-side frameworks see: Survey of AJAX/JavaScript Libraries.
What is the difference between proxied and proxyless calls?
Proxied calls are made through stub objects that mimic your PHP classes on the JavaScript side. E.g., the helloworld class from the Hello World example.
Proxyless calls are made using utility javascript functions like HTML_AJAX.replace() and HTML_AJAX.append().
Should I use XML or text, JavaScript, or HTML as a return type?
It depends. Clearly the ‘X’ in AJAX stands for XML, but several AJAX proponents are quick to point out that nothing in AJAX, per se, precludes using other types of payload, such as, JavaScript, HTML, or plain text.
* XML – Web Services and AJAX seem made for one another. You can use client-side API’s for downloading and parsing the XML content from RESTful Web Services. (However be mindful with some SOAP based Web Services architectures the payloads can get quite large and complex, and therefore may be inappropriate with AJAX techniqes.)
* Plain Text – In this case server-generated text may be injected into a document or evaluated by client-side logic.
* JavaScript – This is an extension to the plain text case with the exception that a server-side component passes a fragment of JavaScript including JavaScript object declarations. Using the JavaScript eval() function you can then create the objects on the client. JavaScript Object Notation (JSON), which is a JavaScript object based data exchange specification, relies on this technique.
* HTML – Injecting server-generated HTML fragments directly into a document is generally a very effective AJAX technique. However, it can be complicated keeping the server-side component in sync with what is displayed on the client.
Mashup is a popular term for creating a completely new web application by combining the content from disparate Web Services and other online API’s. A good example of a mashup is housingmaps.com which graphically combines housing want-ads from craiglist.org and maps from maps.google.com.
Are there Usability Issues with AJAX?
The nature of updating a page dynamically using data retrieved via AJAX interactions and DHTML may result in drastically changing the appearance and state of a page. A user might choose to use the browser’s back or forward buttons, bookmark a page, copy the URL from the URL bar and share it with a friend via an email or chat client, or print a page at any given time. When designing an AJAX based application you need to consider what the expected behavior would be in the case of navigation, bookmarking, printing, and browser support as described below.
* Navigation – What would be the expected behavior of the back, forward, refresh, and bookmark browser buttons in your application design. While you could implement history manipulation manually it may be easer to use a JavaScript frameworks such as Dojo that provides API’s history manipulation and navigation control.
* Bookmarking and URL sharing – Many users want to bookmark or cut and paste the URL from the browser bar. Dojo provides client-side for bookmarking and URL manipulation.
* Printing – In some cases printing dynamically rendered pages can be problematic.
Other considerations as a developer when using AJAX are:
* Browser Support – Not all AJAX/DHTML features are supported on all browsers or all versions of a browser. See quirksmode.org for a list of browser support and possible workarounds.
* JavaScript disabled – You should also consider what happens if the user disables JavaScript. Additionally, there are several legitimate reasons why JavaScript and CSS support may be unavailable on a user’s web browser.
* Latency – Keep in mind latency in your design. A running application will be much more responsive than when it is deployed.
Latency problems: myth or reality?
* Accessibility – Guaranteeing your site is accessible to people with disabilities is not only a noble goal, it is also requited by law in many markets. Some marvelous enabling technology is available to help people use the Web in spite of disabilities including visual, auditory, physical, speech, cognitive, and neurological disabilities. With a little forethought, and comprehension of some well documented best practices, you can assure that your application is compatible with that enabling technology.
Degradability is the term used to describe techniques used by web applications to adapt to the wide range of web browser capabilities. Many AJAX libraries have automatic degradability built in. But if you are coding your own custom AJAX functionality, simply taking some care to follow the best practices promoted by standards bodies like the World Wide Web Consortium (W3C), and grass root movements like the Web Standards community and many others, your application can run usefully on browsers that are incapable of AJAX behaviors. Granted, your application may loose some of the “wow factor” on these less capable browsers, but your application will still be usable.
Remember to not design with AJAX just for the sake of coolness. The reason you built your application is so people will use it. And people will not use your application if your application is not compatible with their web browser.
Are there any frameworks available to help speedup development with AJAX?
There are several browser-side frameworks available, each with their own uniqueness…
Is Adaptive Path selling Ajax components or trademarking the name? Where can I download it?
Ajax isn?t something you can download. It?s an approach ? a way of thinking about the architecture of web applications using certain technologies. Neither the Ajax name nor the approach are proprietary to Adaptive Path.
Should I use an HTTP GET or POST for my AJAX calls?
AJAX requests should use an HTTP GET request when retrieving data where the data will not change for a given request URL. An HTTP POST should be used when state is updated on the server. This is in line with HTTP idempotency recommendations and is highly recommended for a consistent web application architecture.
How do I debug JavaScript?
There are not that many tools out there that will support both client-side and server-side debugging. I am certain this will change as AJAX applications proliferate. I currently do my client-side and server-side debugging separately. Below is some information on the client-side debuggers on some of the commonly used browsers.
* Firefox/Mozilla/Netscape – Have a built in debugger Venkman which can be helpful but there is a Firefox add on known as FireBug which provides all the information and AJAX developer would ever need including the ability to inspect the browser DOM, console access to the JavaScript runtime in the browser, and the ability to see the HTTP requests and responses (including those made by an XMLHttpRequest). I tend to develop my applications initially on Firefox using Firebug then venture out to the other browsers.
* Safari – Has a debugger which needs to be enabled. See the Safari FAQ for details.
* Internet Explorer – There is MSDN Documentation on debugging JavaScript. A developer toolbar for Internet Explorer may also be helpful.
While debuggers help a common technique knowing as “Alert Debugging” may be used. In this case you place “alert()” function calls inline much like you would a System.out.println. While a little primitive it works for most basic cases. Some frameworks such as Dojo provide APIs for tracking debug statements.
How do I provide internationalized AJAX interactions?
Just because you are using XML does not mean you can properly send and receive localized content using AJAX requests. To provide internationalized AJAX components you need to do the following:
* Set the charset of the page to an encoding that is supported by your target languages. I tend to use UTF-8 because it covers the most languages. The following meta declaration in a HTML/JSP page will set the content type:
* In the page JavaScript make sure to encode any parameters sent to the server. JavaScript provides the escape() function which returns Unicode escape strings in which localized text will appear in hexadecimal format. For more details on JavaScript encoding see Comparing escape(), encodeURI(), and encodeURIComponent().
* On the server-side component set the character encoding using the HttpServletRequest.setCharacterEncoding() method. Before you access the localized parameter using the HttpServletRequest.getParameter() call. In the case of UTF this would be request.setCharactherEncoding(“UTF-8”);.
A server-side component returning AJAX responses needs to set the encoding of the response to the same encoding used in the page.
response.setContentType(“text/xml;charset=;UTF-8″);
response.getWriter().write(” invalid “);
For more information on using AJAX with Java Enterprise Edition technologies see AJAX and Internationalization and for developing multi-lingual applications see Developing Multilingual Web Applications Using JavaServer Pages Technology.
Some of the Google examples you cite don?t use XML at all. Do I have to use XML and/or XSLT in an Ajax application?
No. XML is the most fully-developed means of getting data in and out of an Ajax client, but there?s no reason you couldn?t accomplish the same effects using a technology like JavaScript Object Notation or any similar means of structuring data for interchange.
Are Ajax applications easier to develop than traditional web applications?
Not necessarily. Ajax applications inevitably involve running complex JavaScript code on the client. Making that complex code efficient and bug-free is not a task to be taken lightly, and better development tools and frameworks will be needed to help us meet that challenge.
When do I use a synchronous versus a asynchronous request?
Good question. They don’t call it AJAX for nothing! A synchronous request would block in page event processing and I don’t see many use cases where a synchronous request is preferable.
How do I handle concurrent AJAX requests?
With JavaScript you can have more than one AJAX request processing at a single time. In order to insure the proper post processing of code it is recommended that you use JavaScript Closures. The example below shows an XMLHttpRequest object abstracted by a JavaScript object called AJAXInteraction. As arguments you pass in the URL to call and the function to call when the processing is done.
function AJAXInteraction(url, callback) {
var req = init();
req.onreadystatechange = processRequest;
function init() {
if (window.XMLHttpRequest) {
return new XMLHttpRequest();
} else if (window.ActiveXObject) {
return new ActiveXObject(“Microsoft.XMLHTTP”);
}
}
function processRequest () {
if (req.readyState == 4) {
if (req.status == 200) {
if (callback) callback(req.responseXML);
}
}
}
this.doGet = function() {
req.open(“GET”, url, true);
req.send(null);
}
this.doPost = function(body) {
req.open(“POST”, url, true);
req.setRequestHeader(“Content-Type”, ”
application/x-www-form-urlencoded”);
req.send(body);
}
}
function makeRequest() {
var ai = new AJAXInteraction(“processme”,
function() { alert(“Doing Post Process”);});
ai.doGet();
}
The function makeRequest() in the example above creates an AJAXInteraction with a URL to of “processme” and an inline function that will show an alert dialog with the message “Doing Post Process”. When ai.doGet() is called the AJAX interaction is initiated and when server-side component mapped to the URL “processme” returns a document which is passed to the callback function that was specified when the AJAXInteraction was created.
Using this closures insures that the proper callback function associated with a specific AJAX interaction is called. Caution should still be taken when creating multiple closure objects in that make XmlHttpRequests as to there is a limited number of sockets that are used to make requests at any given time. Because there are limited number of requests that can be made concurrently. Internet Explorer for example only allows for two concurrent AJAX requests at any given time. Other browsers may allow more but it is generally between three and five requests. You may choose to use pool of AJAXInteraction objects.
One thing to note when making multiple AJAX calls from the client is that the calls are not guaranteed to return in any given order. Having closures within the callback of a closure object can be used to ensure dependencies are processed correctly.
There is a discussion titled Ajaxian Fire and Forget Pattern that is helpful.
What do I do on the server to interact with an AJAX client?
The “Content-Type” header needs to be set to”text/xml”. In servlets this may be done using the HttpServletResponse.setContentType()should be set to “text/xml” when the return type is XML. Many XMLHttpRequest implementations will result in an error if the “Content-Type” header is set The code below shows how to set the “Content-Type”.
response.setContentType(“text/xml”);
response.getWriter().write(“invalid”);
You may also want to set whether or not to set the caches header for cases such as autocomplete where you may want to notify proxy servers/and browsers not to cache the results.
response.setContentType(“text/xml”);
response.setHeader(“Cache-Control”, “no-cache”);
response.getWriter().write(“invalid”);
Note to the developer: Internet Explorer will automatically use a cached result of any AJAX response from a HTTP GET if this header is not set which can make things difficult for a developer. During development mode you may want set this header. Where do I store state with an AJAX client
As with other browser based web applications you have a few options which include:
* On the client in cookies – The size is limited (generally around 4KB X 20 cookies per domain so a total of 80KB) and the content may not be secure unless encrypted which is difficult but not impossible using JavaScript.
* On the client in the page – This can be done securely but can be problematic and difficult to work with. See my blog entry on Storing State on the Client for more details on this topic.
* On the client file system – This can be done if the client grants access to the browser to write to the local file system. Depending on your uses cases this may be necessary but caution is advised.
* On the Server – This is closer to the traditional model where the client view is of the state on the server. Keeping the data in sync can be a bit problematic and thus we have a solution Refreshing Data on this. As more information processing and control moves to the client where state is stored will need to be re-evaluated.
Whats with the -alpha in the install instructions?
HTML_AJAX hasn’t had a stable release yet and the pear installer doesn’t install non stable packages by default unless you specify a version.
How do I submit a form or a part of a form without a page refresh?
When creating a form make sure that the “form” element “onSubmit” attribute is set to a JavaScript function that returns false.
You can also submit data by associating a function with a form button in a similar way.
Note that the form “onSubmit” attribute is still set. If the user hits the enter key in the text field the form will be submitted so you still need to handle that case.
When updating the page it is recommend you wait to make sure that the AJAX update of the form data was successful before updating the data in the page. Otherwise, the data may not properly update and the user may not know. I like to provide an informative message when doing a partial update and upon a successful AJAX interaction I will then update the page.
How do I test my AJAX code?
There is a port of JUnit for client-side JavaScript called JsUnit
What exactly is the W3C DOM?
The W3C Document Object Model (DOM) is defined by the W3C as the following: The Document Object Model is a platform- and language-neutral interface…
When will HTML_AJAX have a stable release?
Once all the major features are complete and the API has been tested, the roadmap gives an idea of whats left to be done.
What parts of the HTML_AJAX API are stable?
We don’t have a list right now, but most of the API is stable as of 0.3.0. There should be no major changes at this point, though there will be lots of new additions.
What Browsers does HTML_AJAX work with?
As of 0.3.0, all the examples that ship with HTML_AJAX have been verified to work with
* Firefox 1.0+
* Internet Explorer 5.5+ (5.0 should work but it hasn’t been tested)
Most things work with
* Safari 2+
* Opera 8.5+
Is the server or the client in control?
It depends. With AJAX the answer is more in between. Control can be more centralized in a server-side component or as a mix of client-side and server-side controllers.
* Centralized server-side controller – When having a more centralized controller the key is to make sure the data in client-side page is in sync with that of the server. Some applications may keep all the state on the server and push all updates to client DOM via a simple JavaScript controller.
* Client and server-side controllers – This architecture would use JavaScript to do all presentation related control, event processing, page manipulation, and rendering of model data on the client. The server-side would be responsible for things such as business logic and pushing updated model data to the client. In this case the server would not have intimate knowledge of the presentation short of the initial page that would be sent to the client page request.
There are some use cases where an entire AJAX application can be written in a single page. Keep in mind if you choose this type of architecture that navigation and bookmarking should be considered.
Both methods are viable depending on what you are trying to accomplish. I tend to prefer spreading the control across the client and server.
Is Ajax just another name for XMLHttpRequest?
No. XMLHttpRequest is only part of the Ajax equation. XMLHttpRequest is the technical component that makes the asynchronous server communication possible; Ajax is our name for the overall approach described in the article, which relies not only on XMLHttpRequest, but on CSS, DOM, and other technologies.
How do I abort the current XMLHttpRequest?
Just call the abort() method on the request.
What is the minimum version of PHP that needs to be running in order to use HTML_AJAX?
The oldest PHP version i’ve fully tested HTML_AJAX is 4.3.11, but it should run on 4.2.0 without any problems. (Testing reports from PHP versions older then 4.3.11 would be appreciated.)
Why does HTML_AJAX hang on some server installs?
If you run into an HTML_AJAX problem only on some servers, chances are your running into a problem with output compression. If the output compression is handled in the PHP config we detect that and do the right thing, but if its done from an apache extension we have no way of knowing its going to compress the body. Some times setting HTML_AJAX::sendContentLength to false fixes the problem, but in other cases you’ll need to disabled the extension for the AJAX pages.
I’ve also seen problems caused by debugging extensions like XDebug, disabling the extension on the server page usually fixes that. Questions dealing with Using HTML_AJAX, and general JavaScript development
How do I get the XMLHttpRequest object?
Depending upon the browser… if (window.ActiveXObject) { // Internet Explorer http_request = new ActiveXObject(“Microsoft.XMLHTTP”); } else if…
Are there any security issues with AJAX?
JavaScript is in plain view to the user with by selecting view source of the page. JavaScript can not access the local filesystem without the user’s permission. An AJAX interaction can only be made with the servers-side component from which the page was loaded. A proxy pattern could be used for AJAX interactions with external services.
You need to be careful not to expose your application model in such as way that your server-side components are at risk if a nefarious user to reverse engineer your application. As with any other web application, consider using HTTPS to secure the connection when confidential information is being exchanged.
What about applets and plugins ?
Don’t be too quick to dump your plugin or applet based portions of your application. While AJAX and DHTML can do drag and drop and other advanced user interfaces there still limitations especially when it comes to browser support. Plugins and applets have been around for a while and have been able to make AJAX like requests for years. Applets provide a great set of UI components and APIs that provide developers literally anything.
Many people disregard applets or plugins because there is a startup time to initialize the plugin and there is no guarantee that the needed version of a plugin of JVM is installed. Plugins and applets may not be as capable of manipulating the page DOM. If you are in a uniform environment or can depend on a specific JVM or plugin version being available (such as in a corporate environment) a plugin or applet solution is great.
One thing to consider is a mix of AJAX and applets or plugins. Flickr uses a combination of AJAX interactions/DHTML for labeling pictures and user interaction and a plugin for manipulating photos and photo sets to provide a great user experience. If you design your server-side components well they can talk to both types of clients.
Why did you feel the need to give this a name?
I needed something shorter than ?Asynchronous JavaScript+CSS+DOM+XMLHttpRequest? to use when discussing this approach with clients.
Is AJAX code cross browser compatible?
Not totally. Most browsers offer a native XMLHttpRequest JavaScript object, while another one (Internet Explorer) require you to get it as an ActiveX object….
Techniques for asynchronous server communication have been around for years. What makes Ajax a ?new? approach?
What?s new is the prominent use of these techniques in real-world applications to change the fundamental interaction model of the Web. Ajax is taking hold now because these technologies and the industry?s understanding of how to deploy them most effectively have taken time to develop.
Is Ajax a technology platform or is it an architectural style?
It?s both. Ajax is a set of technologies being used together in a particular way.
How do I handle the back and forward buttons?
While you could go out and create a custom solution that tracks the current state on your application I recommend you leave this to the experts. Dojo addresses the navigation in a browser neutral way as can be seen in the JavaScript example below.
function updateOnServer(oldId, oldValue,
itemId, itemValue) {
var bindArgs = {
url: “faces/ajax-dlabel-update”,
method: “post”,
content: {“component-id”: itemId, “component-value”:
itemValue},
mimetype: “text/xml”,
load: function(type, data) {
processUpdateResponse(data);
},
backButton: function() {
alert(“old itemid was ” + oldId);
},
forwardButton: function(){
alert(“forward we must go!”);
}
};
dojo.io.bind(bindArgs);
}
The example above will update a value on the server using dojo.io.bind() with a function as a property that is responsible for dealing with the browser back button event. As a developer you are capable of restoring the value to the oldValue or taking any other action that you see fit. The underlying details of how the how the browser button event are detected are hidden from the developer by Dojo.
AJAX: How to Handle Bookmarks and Back Buttons details this problem and provides a JavaScript library Really Simple History framework (RSH) that focuses just on the back and forward issue.
How does HTML_AJAX compare with the XAJAX project at Sourceforge?
XAJAX uses XML as a transport for data between the webpage and server, and you don’t write your own javascript data handlers to manipulate the data received from the server. Instead you use a php class and built in javascript methods, a combination that works very similiar to the HTML_AJAX_Action class and haSerializer combo. XAJAX is designed for simplicity and ease of use.
HTML_AJAX allows for multiple transmission types for your ajax data – such as urlencoding, json, phpserialized, plain text, with others planned, and has a system you can use to write your own serializers to meet your specific needs. HTML_AJAX has a class to help generate javascript (HTML_AJAX_Helper) similiar to ruby on rail’s javascript helper (although it isn’t complete), and an action system similiar to XAJAX’s “action pump” that allows you to avoid writing javascript data handlers if you desire.
But it also has the ability to write your own data handling routines, automatically register classes and methods using a server “proxy” script, do different types of callbacks including grabbing remote urls, choose between sync and async requests, has iframe xmlhttprequest emulation fallback capabilities for users with old browsers or disabled activeX, and is in active development with more features planned (see the Road Map for details)
HTML_AJAX has additional features such as client pooling and priority queues for more advanced users, and even a javascript utility class. Although you can use HTML_AJAX the same way you use XAJAX, the additional features make it more robust, extensible and flexible. And it is a pear package, you can use the pear installer to both install and keep it up to date.
If you’re asking which is “better” – as with most php scripts it’s a matter of taste and need. Do you need a quick, simple ajax solution? Or do you want something that’s flexible, extensible, and looking to incorporate even more great features? It depends on the project, you as a writer, and your future plans.
What browsers support AJAX?
Internet Explorer 5.0 and up, Opera 7.6 and up, Netscape 7.1 and up, Firefox 1.0 and up, Safari 1.2 and up, among others.
How do I send an image using AJAX?
While it may appear that images are being sent when using AJAX with an application like Google Maps what is really happening is that the URLs of images are being send as the response of an AJAX request and those URLs are being set using DHTML.
In this example an XML document is returned from an AJAX interaction and the category bar is populated.
1
Books
Fun to read
books_icon.gif
2
Electronics
Must have gadgets
electronics.gif
Notice that the image-url element contains the location of the URL for the image representing a category. The callback method of an AJAX interaction will parse the response XML document and call the addCategory function for each category included in the response XML document. The addCategory function looks up a table row element “categoryTable” in body of the page and adds a row to the element which contains the image.

function addCategory(id, name, imageSrc) {
var categoryTable = document.getElementById(“categoryTable”);
var row = document.createElement(“tr”);
var catCell = document.createElement(“td”);
var img = document.createElement(“img”);
img.src = (“images\\” + imageSrc);
var link = document.createElement(“a”);
link.className =”category”;
link.appendChild(document.createTextNode(name));
link.setAttribute(“onclick”, “catalog?command=category&catid=” + id);
catCell.appendChild(img);
catCell.appendChild(link);
row.appendChild(catCell);
categoryTable.appendChild(row);
}

  Body Here

Note that the source of the image is set to the image source. The image is loaded by a subsequent HTTP request for the image at the URL “images/books_icon.gif” or “images/electronic_icon.gif” that occurs when the img element is added to the categoryTable.
Will HTML_AJAX integrate with other Javascript AJAX libraries such as scriptaculous ? How would this integration look like?
HTML_AJAX doesn’t have specific plans to integrate with other JavaScript libraries. Part of this is because external dependencies make for a more complicated installation process. It might make sense to offer some optional dependencies on a library like scriptaculous automatically using its visual effects for the loading box or something, but there isn’t a lot to gain from making default visuals like that flashier since they are designed to be easily replaceable.
Most integration would take place in higher level components. Its unclear whether higher level components like that should be part of HTML_AJAX delivered through PEAR or if they should just be supported by HTML_AJAX and made available from http://htmlajax.org or some other site. If your interested in building widgets or components based on HTML_AJAX please let me know.
HTML_AJAX does however offer the ability to use its library loading mechanism with any JavaScript library. I use scriptaculous in conjunction with HTML_AJAX and I load both libraries through the server.
To do this you just need to register the library with your server and load add its flag to your include line.
server->registerJSLibrary(‘scriptaculous’,
array(‘prototype.js’,’scriptaculous.js’,’builder.js’,’effects.js’,’dragdrop.js’,’controls.js’,’slider.js’), ‘/pathto/scriptaculous/’);?>
When should I use an Java applet instead of AJAX?
Applets provide a rich experience on the client side and there are many things they can do that an AJAX application cannot do, such as custom data streaming, graphic manipulation, threading, and advanced GUIs. While DHTML with the use of AJAX has been able to push the boundaries on what you can do on the client, there are some things that it just cannot do. The reason AJAX is so popular is that it only requires functionality built into the browser (namely DHTML and AJAX capabilities). The user does not need to download and/or configure plugins. It is easy to incrementally update functionality and know that that functionality will readily available, and there are not any complicated deployment issues. That said, AJAX-based functionality does need to take browser differences into consideration. This is why we recommend using a JavaScript library such as Dojo which abstracts browser differences. So the “bottom line” is: If you are creating advanced UIs where you need more advanced features on the client where you want UI accuracy down to the pixel, to do complex computations on the client, use specialized networking techniques, and where you know that the applet plugin is available for your target audience, applets are the way to go. AJAX/DHTML works well for applications where you know the users are using the latest generation of browsers, where DHTML/AJAX “good enough” for you, and where your developers have JavaScript/DHTML/AJAX skills. Many amazing things can be done with AJAX/DHTML but there are limitations. AJAX and applets can be used together in the same UIs with AJAX providing the basic structure and applets providing more advanced functionality. The Java can communicate to JavaScript using the Live-Connect APIs. The question should not be should framed as do I use AJAX or applets, but rather which technology makes the best sense for what you are doing. AJAX and applets do not have to be mutually exclusive.
What kinds of applications is Ajax best suited for?
We don?t know yet. Because this is a relatively new approach, our understanding of where Ajax can best be applied is still in its infancy. Sometimes the traditional web application model is the most appropriate solution to a problem.
Does this mean Adaptive Path is anti-Flash?
Not at all. Macromedia is an Adaptive Path client, and we?ve long been supporters of Flash technology. As Ajax matures, we expect that sometimes Ajax will be the better solution to a particular problem, and sometimes Flash will be the better solution. We?re also interested in exploring ways the technologies can be mixed (as in the case of Flickr, which uses both).
Where can I find examples of AJAX?
While components of AJAX have been around for some time (for instance, 1999 for XMLHttpRequest), it really didn’t become that popular until Google took…
What is the XMLHttpRequest object?
It offers a non-blocking way for JavaScript to communicate back to the web server to update only part of the web page.
Does Ajax have significant accessibility or browser compatibility limitations? Do Ajax applications break the back button? Is Ajax compatible with REST? Are there security considerations with Ajax development? Can Ajax applications be made to work for users who have JavaScript turned off?
The answer to all of these questions is ?maybe?. Many developers are already working on ways to address these concerns. We think there?s more work to be done to determine all the limitations of Ajax, and we expect the Ajax development community to uncover more issues like these along the way.
How do I access data from other domains to create a mashup with Java?
From your JavaScript clients you can access data in other domains if the return data is provide in JSON format. In essence you can create a JavaScript client that runs operates using data from a different server. This technique is know as JSON with Padding or JSONP. There are questions as to whether this method is secure as you are retrieving data from outside your domain and allowing it to be excuted in the context of your domain. Not all data from third parties is accessible as JSON and in some cases you may want an extra level of protection. With Java you can provide a proxy to third party services using a web component such as a servlet. This proxy can manage the communication with a third party service and provide the data to your clients in a format of your choosing. You can also cache data at your proxy and reduce trips to service. For more on using a Java proxy to create mashups see The XmlHttpProxy Client for Java.
Does Java have support for Comet style server-side push?
Current AJAX applications use polling to communicate changes data between the server and client. Some applications, such as chat applications, stock tickers, or score boards require more immediate notifications of updates to the client. Comet is an event based low latency server side push for AJAX applications. Comet communication keeps one of the two connections available to the browser open to continously communicate events from the server to the client. A Java based solution for Comet is being developed for Glassfish on top of the Grizzly HTTP connector. See Enabling Grizzly by Jean-Francois Arcand for more details.
How do I create a thread to do AJAX polling?
JavaScript does not have threads. JavaScript functions are called when an event happens in a page such as the page is loaded, a mouse click, or a form element gains focus. You can create a timer using the setTimeout which takes a function name and time in milliseconds as arguments. You can then loop by calling the same function as can be seen in the JavaScript example below.
function checkForMessage() {
// start AJAX interaction with processCallback as the callback function
}
// callback for the request
function processCallback() {
// do post processing
setTimeout(“checkForMessage()”, 10000);
}
Notice that the checkForMessage will continue to loop indefinitely. You may want to vary the increment the interval based on activity in the page or your use cases. You may also choose to have logic that would break out of the loop based on some AJAX response processing condition.
Is the XMLHttpRequest object part of a W3C standard?
No. Or not yet. It is part of the DOM Level 3 Load and Save Specification proposal.

Categories
HTML PHP XML

CSS Interview Questions And Answers – important good answers

Which set of definitions, HTML attributes or CSS properties, take precedence?
CSS properties take precedence over HTML attributes. If both are specified, HTML attributes will be displayed in browsers without CSS support but won’t have any effect in browsers with CSS support.
How do I eliminate the blue border around linked images?
in your CSS, you can specify the border property for linked images:
a img { border: none ; }
However, note that removing the border that indicates an image is a link makes it harder for users to distinguish quickly and easily which images on a web page are clickable.
Why call the subtended angle a “pixel”, instead of something else (e.g. “subangle”)?
In most cases, a CSS pixel will be equal to a device pixel. But, as you point out, the definition of a CSS pixel will sometimes be different. For example, on a laser printer, one CSS pixel can be equal to 3×3 device pixels to avoid printing illegibly small text and images. I don’t recall anyone ever proposing another name for it. Subangle? Personally, I think most people would prefer the pragmatic “px” to the non-intuitive “sa”.
Why was the decision made to make padding apply outside of the width of a ‘box’, rather than inside, which would seem to make more sense?
It makes sense in some situations, but not in others. For example, when a child element is set to width: 100%, I don’t think it should cover the padding of its parent. The box-sizing property in CSS3 addresses this issue. Ideally, the issue should have been addressed earlier, though.
How to use CSS to separate content and design ?
The idea here is that all sites contain two major parts, the content: all your articles, text and photos and the design: rounded corners, colors and effects. Usually those two are made in different parts of a webpage?s lifetime. The design is determined at the beginning and then you start filling it with content and keep the design fixed.
In CSS you just add the nifty -tag I’ve told you about to the head of your HTML document and you have created a link to your design. In the HTML document you put content only, and that link of yours makes sure it looks right. You can also use the exact same link on many of your pages, giving them all of them the same design. You want to add content? Just write a plain HTML document and think about marking things up like ?header? instead of ?big blue header? and use CSS to make all headers look the way you want!
Some examples of good and bad coding. What’s wrong with this?
Welcome to my page
Comment: The font-tag is design and design shouldn?t be in the HTML document. All design should be in the CSS-file! Instead do this:
In the HTML:

Welcome to my page

In the CSS:
h1 { font-size: 2em; }
One more example:
An error occurred
This looks right doesn?t it? But if you look up what stands for you quickly find bold. But bold is certainly design, so it still doesn?t belong in the HTML document. A better choice is that stands for emphasis or simply ?this piece of text is important?. So instead of saying ?this text looks like this? you are saying ?this text is important? and you let the looks be decided by the CSS. Seems like a minor change, but it illustrates how to select your tags. Use this instead:

In the HTML:
An error occured
In the CSS:
em {
font-weight: bold;
color: Red;
}
One last example:

first link
second link

Can CSS be used with other than HTML documents?
Yes. CSS can be used with any ny structured document format. e.g. XML, however, the method of linking CSS with other document types has not been decided yet.
Can Style Sheets and HTML stylistic elements be used in the same document?
Yes. Style Sheets will be ignored in browsers without CSS-support and HTML stylistic elements used.
What are pseudo-classes?
Pseudo-classes are fictional element types that do not exist in HTML. In CSS1 there is only one element type which can be classed this way, namely the A element (anchor). By creating three fictional types of the A element individual style can be attached to each class. These three fictional element types are: A as unvisited link, A as active link and A as visited link. Pseudo-classes are created by a colon followed by pseudo-class’s name. They can also be combined with normal classes, e.g.:
A:link {background: black; color: white}
A:active {background: black; color: red}
A:visited {background: transparent; color: black}
This anchor (or rather these anchors) will be displayed as declared above
A.foot:link {background: black; color: white}
A.foft:active {background; black: color: red}
A.foot:visited {background: transparent; color: black}
This anchor and all other anchors with CLASS foot will be displayed as declared above
How do I design for backward compatibility using Style Sheets?
Existing HTML style methods (such as and ) may be easily combined with style sheet specification methods. Browsers that do not understand style sheets will use the older HTML formatting methods, and style sheets specifications can control the appearance of these elements in browsers that support CSS1.
As a reader, how can I make my browser recognize my own style sheet?
Netscape
It is not possible to do this in Netscape yet (as of version 4.0.)
Internet Explorer 3.0 (Win95/NT)
[It is possible to do this at least in Windows95/NT, but no user interface is provided. Unknown how this might be accomplished on other operating systems.]

1. Open the Registry editor (Start..Run..regedit..ENTER)
2. Under the ‘HKEY_LOCAL_MACHINE\Software\Microsoft\InternetExplorer\Styles’ key, Edit..New..String Value
3. The new value should be called ‘StyleSheet Pathname’
4. For the value, type in the full directory path of your .css style sheet.

Internet Explorer 4.0 (Win95/NT)
1. Under the View menu, select ‘Internet Options’.
2. Under the ‘General’ tab, choose the ‘Accessibility’ button.
3. Choose the ‘Format documents using my style sheet’ check box and ‘Browse…’ to the location of your .css style sheet.

How do I get rid of the gap under my image?
Images are inline elements, which means they are treated in the same way as text. Most people kind of know this – they know that if you use ‘text-align:center’ on an image it will be centred. What many people don’t realise is that this means you will have a gap underneath an image. This gap is for the descenders of letters like j,q,p,y and g. To get rid of this gap you need to make the image block-level – like this :

CSS
img {display:block;}

One problem that this can cause is when you want to have a few images next to each other – if they are block-level, they won’t be next to each other. To get around that, you can use float:left. Of course, this might present another problem – maybe you don’t want the image to float left. In this case, you can use an unordered list like this :
CSS
ul, li {
list-style-type:none;
padding:0;
margin:0 auto;
}
ul {
width:150px;
}
li {
float:left;
}
HTML


Why use Style Sheets?
Style sheets allow a much greater degree of layout and display control than has ever been possible thus far in HTML. The amount of format coding necessary to control display characteristics can be greatly reduced through the use of external style sheets which can be used by a group of documents. Also, multiple style sheets can be integrated from different sources to form a cohesive tapestry of styles for a document. Style sheets are also backward compatible – They can be mixed with HTML styling elements and attributes so that older browsers can view content as intended.

What does the “Cascading” in “Cascading Style Sheets” mean?
Style Sheets allow style information to be specified from many locations. Multiple (partial) external style sheets can be referenced to reduce redundancy, and both authors as well as readers can specify style preferences. In addition, three main methods can be employed by an author to add style information to HTML documents, and multiple approaches for style control are available in each of these methods. In the end, style can be specified for a single element using any, or all, of these methods. What style is to be used when there is a direct conflict between style specifications for an element?
Cascading comes to the rescue. A document can have styles specified using all of these methods, but all the information will be reduced to a single, cohesive “virtual” Style Sheet. Conflict resolution is based on each style rule having an assigned weight according to its importance in the scheme of things. A rule with a higher overall importance will carry a higher weight. This will be used in place of a competing style rule with a lower weight/importance. A hierarchy of competing styles is thus formed creating a “cascade” of styles according to their assigned weights. The algorithm used to determine this cascading weight scale is fairly complex.

What is CSS rule ‘at-rule’?
There are two types of CSS rules: ruleset and at-rule. At-rule is a rule that applies to the whole style sheet and not to a specific selector only (like in ruleset). They all begin with the @ symbol followed by a keyword made up of letters a-z, A-Z, digits 0-9, dashes and escaped characters, e.g. @import or @font-face.

What is selector?
CSS selector is equivalent of HTML element(s). It is a string identifying to which element(s) the corresponding declaration(s) will apply and as such the link between the HTML document and the style sheet.
For example in P {text-indent: 10pt} the selector is P and is called type selector as it matches all instances of this element type in the document.
in P, UL {text-indent: 10pt} the selector is P and UL (see grouping); in .class {text-indent: 10pt} the selector is .class (see class selector).

What is CLASS selector?
Class selector is a “stand alone” class to which a specific style is declared. Using the CLASS attribute the declared style can then be associated with any HTML element. The class selectors are created by a period followed by the class’s name. The name can contain characters a-z, A-Z, digits 0-9, period, hyphen, escaped characters, Unicode characters 161-255, as well as any Unicode character as a numeric code, however, they cannot start with a dash or a digit. (Note: in HTML the value of the CLASS attribute can contain more characters).It is a good practice to name classes according to their function than their appearance.

.footnote {font: 70%} /* class as selector */

This element is associated with the CLASS footnote


And so is this

What is CSS declaration?
CSS declaration is style attached to a specific selector. It consists of two parts; property which is equivalent of HTML attribute, e.g. text-indent: and value which is equivalent of HTML value, e.g. 10pt. NOTE: properties are always ended with a colon.

What is ‘important’ declaration?
Important declaration is a declaration with increased weight. Declaration with increased weight will override declarations with normal weight. If both reader’s and author’s style sheet contain statements with important declarations the author’s declaration will override the reader’s.

BODY {background: white ! important; color: black}
In the example above the background property has increased weight while the color property has normal.
What is cascade?
Cascade is a method of defining the weight (importance) of individual styling rules thus allowing conflicting rules to be sorted out should such rules apply to the same selector.

Declarations with increased weight take precedence over declaration with normal weight:
P {color: white ! important} /* increased weight */
P (color: black} /* normal weight */

Are Style Sheets case sensitive?
No. Style sheets are case insensitive. Whatever is case insensitive in HTML is also case insensitive in CSS. However, parts that are not under control of CSS like font family names and URLs can be case sensitive – IMAGE.gif and image.gif is not the same file.

How do I make my div 100% height?
You need to know what the 100% is of, so the parent div must have a height set. One problem that people often come up against is making the main page fill the screen if there’s little content. You can do that like this :
CSS
body, html {
height:100%;
}
body {
margin:0;
padding:0;
}
#wrap {
position:relative;
min-height:100%;
}
* html #wrap {
height:100%;
}

Here, the #wrap div goes around your whole page – it’s like a sub-body.
You need to use ‘min-height’ rather than ‘height’ for Firefox because otherwise it will set it to 100% of the viewport and no more. Internet Explorer, being well… crap, treats ‘height’ as it should be treating ‘min-height’ which it doesn’t recognise. (You can target IE by preceding your code with ‘ * html ‘).
To make floated divs within this #wrap div 100% of the #wrap div… well that’s more difficult. I think the best way is to use the ‘faux columns’ technique which basically means that you put the background in your body rather than your columns. If the body has columns and your floats don’t then it looks like your floated content is in a column that stretches to the bottom of the page. I’ve used this technique in my layout demos.
The problem is often not that the columns aren’t 100% height, but that they’re not equal lengths. Columns usually don’t start from the top of the page and end at the bottom – there’s often a header and a footer or sometimes, more interesting designs don’t have a recognisable columnar layout, but do require div boxes to be equal heights. This can be done with the aid of a couple of images and some css or with some javascript.
What is property?
Property is a stylistic parameter (attribute) that can be influenced through CSS, e.g. FONT or WIDTH. There must always be a corresponing value or values set to each property, e.g. font: bold or font: bold san-serif.

How do I write my style sheet so that it gracefully cascades with user’s personal sheet ?
You can help with this by setting properties in recommended places. Style rules that apply to the whole document should be set in the BODY element — and only there. In this way, the user can easily modify document-wide style settings.

What are pseudo-elements?
Pseudo-elements are fictional elements that do not exist in HTML. They address the element’s sub-part (non-existent in HTML) and not the element itself. In CSS1 there are two pseudo-elements: ‘first-line pseudo-element’ and ‘first-letter pseudo-element’. They can be attached to block-level elements (e.g. paragraphs or headings) to allow typographical styling of their sub-parts. Pseudo-element is created by a colon followed by pseudo-element’s name, e.g:

P:first-line
H1:first-letter

and can be combined with normal classes; e.g:
P.initial:first-line
First-line pseudo-element allows sub-parting the element’s first line and attaching specific style exclusively to this sub-part; e.g.:
P.initial:first-line {text-transform: uppercase}

The first line of this paragraph will be displayed in uppercase letters

First-letter pseudo-element allows sub-parting the element’s first letter and attaching specific style exclusively to this sub-part; e.g.:
P.initial:first-letter { font-size: 200%; color: red}

The first letter of this paragraph will be displayed in red and twice as large as the remaining letters

As a developer who works with CSS every day, I find one complication that continues to bother me in my daily work. Support for CSS has always been good on the horizontal scope, but vertical positioning has always been quite complicated. Alone the procedure to affix a footer to the bottom of a screen in dependance of the amount of content is unnecessarily difficult. The old table method provided much easier methods for this. What are your thoughts on this and do you see improvement following in future CSS revisions?
Indeed, the CSS formatting model allows more control horizontally than vertically. This is due to (typically) having a known width, but an unknown height. As such, the height is harder to deal with. However, CSS2 fixed positioning allows you to place content relative to the viewport (which is CSS-speak for window) instead of the document. For example, by setting position: fixed; bottom: 0 on an element, it will stick to the bottom. This works in Opera, Safari and Mozilla-based browsers. IE6 doesn’t support it, however. It remains to be seen if IE7 will support it.

How can I make a page look the same in e.g. NS and MSIE ?
The simple answer is, you can’t, and you shouldn’t waste your time trying to make it exactly the same. Web browsers are allowed, per definition, to interpret a page as they like, subject to the general rules set down in the HTML and CSS specifications. As a web author you can not have a prior knowledge of the exact situation and/or medium that will be used to render your page, and it’s almost always rather counterproductive to try to control that process. There is no necessity for a well-written page to look the same in different browsers. You may want to strive to ensure that it looks good in more than one browser, even if the actual display (in the case of graphical browsers) comes out a bit different. “Looking good” can be achieved by adopting sensible design and guidelines, such as not fixing the size or face of your fonts, not fixing the width of tables, etc? Don’t fight the medium; most web users only use one browser and will never know, or bother to find out, that your page looks different, or even “better”, in any other browser.

Is there anything that CAN’T be replaced by Style Sheets?
Quite a bit actually. Style sheets only specify information that controls display and rendering information. Virtual style elements that convey the NATURE of the content can not be replaced by style sheets, and hyperlinking and multimedia object insertion is not a part of style sheet functionality at all (although controlling how those objects appear IS part of style sheets functionality.) The CSS1 specification has gone out of its way to absorb ALL of the HTML functionality used in controlling display and layout characteristics. For more information on the possible properties in CSS, see the Index DOT Css Property Index.
Rule of Thumb: if an HTML element or attribute gives cues as to how its contents should be displayed, then some or all of its functionality has been absorbed by style sheets.

Can I include comments in my Style Sheet?
Yes. Comments can be written anywhere where whitespace is allowed and are treated as white space themselves. Anything written between /* and */ is treated as a comment (white space). NOTE: Comments cannot be nested.

What is the difference between ID and CLASS?
ID identifies and sets style to one and only one occurrence of an element while class can be attached to any number of elements. By singling out one occurrence of an element the unique value can be declared to said element.

CSS
#eva1 {background: red; color: white}
.eva2 {background: red; color: white}

HTML – ID

Paragraph 1 – ONLY THIS occurrence of the element P (or single occurrence of some other element) can be identified as eva1

Paragraph 2 – This occurrence of the element P CANNOT be identified as eva1
HTML – CLASS

Paragraph 1 – This occurrence of the element P can be classified as eva2


Paragraph 2 – And so can this, as well as occurrences of any other element,

How to make text-links without underline?
a:link, a:visited {text-decoration: none}

or

…will show the links without underlining. However, suppressing the underlining of links isn’t a very smart idea as most people are used to having them underlined. Also, such links are not spotted unless someone coincidentally runs a mouse over them. If, for whatever reason, links without underline are required background and foreground colors can be instead declared to them so that they can be distinguished from other text, e.g.;
a:link, a:visited {text-decoration: none; background: red; color: blue}
or

Both background and foreground colors should be specified as the property that is not specified can be overridden by user’s own settings.
How do you make a tool tip that appears on hover?
The most simple way is to use the ‘title’ attribute like this…

HTML
like this
CSS
a.tooltip {
position:relative;
cursor:help;
}
a.tooltip span {
display: none;
position:absolute;
top:1.5em;
left:0;
width:15em;
padding:0 2px;
}
a.tooltip:hover {
display:inline;
}
a.tooltip:hover span {
display:block;
border:1px solid gray;
background-color:white;
}

HTML
Karl Marx-info goes here-
Without this part… a.tooltip:hover {
display:inline;
}

..it won’t work in IE.
The “#n” in the link is to prevent the page from jumping to the top if the link is clicked. The “href” part is necessary as it won’t work in IE without it.
Which characters can CSS-names contain?
The CSS-names; names of selectors, classes and IDs can contain characters a-z, A-Z, digits 0-9, period, hyphen, escaped characters, Unicode characters 161-255, as well as any Unicode character as a numeric code. The names cannot start with a dash or a digit. (Note: in HTML the value of the CLASS attribute can contain more characters).

What browsers support style sheets? To what extent?
Microsoft’s Internet Explorer version 3.0 Beta 2 and above supports CSS, as does Netscape Communicator 4.0 Beta 2 and above and Opera 3.5 and above. Take note that the early implementations in these browsers did not support ALL of the properties and syntax described in the full CSS1 specification and beyond. Later versions have been getting much closer to full CSS1 compliance, but then comes the next hurdle – CSS2…it was such a big leap over CSS1 that it has taken the browsers years to come close to supporting a majority of CSS2’s features. Mozilla and Opera’s current versions both offer excellent CSS standards compliance. The Macintosh version of Internet Explorer is said to be very impressive in its CSS capabilities as well, but PC IE lags behind these implementations. Quite a few other implementations of CSS now exist in browsers that are not as widely-used (such as Amaya, Arena and Emacs-W3), but coverage of features in these documents currently only covers Internet Explorer, NCSA Mosaic, Netscape and Opera browsers.

What is cascading order?
Cascading order is a sorting system consisting of rules by which declarations are sorted out so that there are not conflicts as to which declaration is to influence the presentation. The sorting begins with rule no 1. If a match is found the search is over. If there is no match under rule no 1 the search continues under rule no 2 and so on.

1. Find all declarations that apply to a specific selector/property and Declare the specified style if the selector matches the element if there isn’t any Let the element inherit its parent property if there isn’t any Use initial value
2. Sort by weight (! important) Increased weight take precedence over normal weight
3. Sort by origin Rules with normal weight declared in author’s style sheet will override rules with normal weight declared in user’s personal style sheets Rules with increased weight declared in user’s personal style sheet will override rules with normal weight declared in author’s style sheet Rules with increased weight declared in author’s style sheet will override rules with increased weight declared in user’s personal style sheets Author’s and user’s rules will override UA’s default style sheet.
4. Sort by selector’s specificity More specific selector will override less specific one: ID-selector (most specific), followed by Classified contextual selectors (TABLE P EM.fot) Class selectors (EM.fot) Contextual selectors – the “lower down” the more weight, (TABLE P EM), (TABLE P EM STRONG) – STRONG has more weight than EM.
5. Sort by order specified If two rules have the same weight, the latter specified overrides ones specified earlier. Style sheets are sorted out as follows: The STYLE attribute (inline style) overrides all other styles The Style element (embedded style) overrides linked and imported sheets The LINK element (external style) overrides imported style The @import statement – imported style sheets also cascade with each other in the same order as they are imported
Why shouldn’t I use fixed sized fonts ?
Only in very rare situations we will find users that have a “calibrated” rendering device that shows fixed font sizes correct. This tells us that we can never know the real size of a font when it’s rendered on the user end. Other people may find your choice of font size uncomfortable. A surprisingly large number of people have vision problems and require larger text than the average. Other people have good eyesight and prefer the advantage of more text on the screen that a smaller font size allows. What is comfortable to you on your system may be uncomfortable to someone else. Browsers have a default size for fonts. If a user finds this inappropriate, they can change it to something they prefer. You can never assume that your choice is better for them. So, leave the font size alone for the majority of your text. If you wish to change it in specific places (say smaller text for a copyright notice at the bottom of page), use relative units so that the size will stay in relationship to what the user may have selected already. Remember, if people find your text uncomfortable, they will not bother struggling with your web site. Very few (if any) web sites are important enough to the average user to justify fighting with the author’s idea of what is best.

How do you make a whole div into a link?
You can’t put ‘a’ tags around a div, but you can do this with javascript :

HTML

… stuff goes here …

If you want to use an empty div with a background image as a link instead of putting your image into the html, you can do something like this:
CSS
#empty {
background-image:url(wine.jpg);
width:50px;
height:50px;
margin:auto;
}
#empty a {
display:block;
height:50px;
}
* html #empty a {
display:inline-block;
}

HTML

How do I have links of different colors on the same page?
Recommending people to use classes in their ‘a’ tags like this :

CSS
a.red {
color:red;
}
a.blue {
color:blue;
}

HTML
A red link
A blue link
This is a valid way to do it, but usually, this isn’t what a page looks like – two links next to each other with different colours – it’s usually something like a menu with one kind of link and main body text or another menu with different links. In this (normal) situation, To go higher up the cascade to style the links. Something like this :
CSS
a {
color:red;
}
#menu a {
color:blue;
}

HTML

There’s a blue link here.

What is shorthand property?
Shorthand property is a property made up of individual properties that have a common “addressee”. For example properties: font-weight, font-style, font-variant, font-size, font-family, refer to the font. To reduce the size of style sheets and also save some keystrokes as well as bandwidth they can all be specified as one shorthand property font, e.g.:

H1 {font-weight: bold;
font-style: italic;
font-variant: small-caps;
font-size: 160%;
font-family: serif}

can be all shorthanded to a space separated list:
H1 {font: bold italic small-caps 160% serif}
Note: To make things even simpler the line-height property can be specified together with the font-size property:
H1 {font: bold italic small-caps 160%/170% serif}
How to use CSS building a standards based HTML template?
It should:
1. Contain: header, navigation, content, footer
2. Use well-structured HTML
3. Be error-free and encourage good coding

Let?s start with number one there:
HTML document split up in four parts all with different meaning, use the
-tag. Div is short for ?division? and isn?t header, navigation and so on …

!DOCTYPE html PUBLIC “-//W3C//DTD HTML 4.01//EN”>
Your own page title

Content

Some sample content, add your own here

body {
background-color: Green;
}
div {
border: 3px solid Black;
padding: 7px;
width: 600px;
}
h1, h2, h3, h4, h5, h6 {
margin: 0;
}

#navigation {
float: left;
width: 150px;
}
#content {
float: left;
width: 430px;
}
#footer {
clear: both;
}

What is value?
Value is a ‘physical’ characteristic of the property. Property declares what should be formatted, e.g. FONT while value suggests how the property should be formatted, e.g. 12pt. By setting the value 12pt to the property FONT it is suggested that the formatted text be displayed in a 12 point font. There must always be a corresponding property to each value or set of values.

H1 {font: bold 180%}
In the example above the H1 selector is declared the FONT property which in its turn is declared the values BOLD and 180%.
The values suggesting alternatives are specified in a comma separated list, e.g.
H1 {font-family: font1, font2}

What is initial value?
Initial value is a default value of the property, that is the value given to the root element of the document tree. All properties have an initial value. If no specific value is set and/or if a property is not inherited the initial value is used. For example the background property is not inherited, however, the background of the parent element shines through because the initial value of background property is transparent.

Hello World


Content of the element P will also have red background
How frustrating is it to write a specification knowing that you’re at the browser vendors’ mercy?
That’s part of the game. I don’t think any specification has a birthright to be fully supported by all browsers. There should be healthy competition between different specifications. I believe simple, author-friendly specifications will prevail in this environment.
Microformats are another way of developing new formats. Instead of having to convince browser vendors to support your favorite specification, microformats add semantics to HTML through the CLASS attribute. And style it with CSS.

How far can CSS be taken beyond the web page–that is, have generalized or non-web specific features for such things as page formatting or type setting?
Yes, it’s possible to take CSS further in several directions. W3C just published a new Working Draft which describes features for printing, e.g., footnotes, cross-references, and even generated indexes.
Another great opportunity for CSS is Web Applications. Just like documents, applications need to be styled and CSS is an intrinsic component of AJAX. The “AJAX” name sounds great.

How To Style Table Cells?
Margin, Border and Padding are difficult to apply to inline elements. Officially, the


 
 

tag is a block level element because it can contain other block level elements (see Basics – Elements).
If you need to set special margins, borders, or padding inside a table cell, then use this markup: yourtext

to apply the CSS rules to the div inside the cell.
How To Style Forms?
Forms and form elements like SELECT, INPUT etc. can be styled with CSS – partially.
Checkboxes and Radiobuttons do not yet accept styles, and Netscape 4.xx has certain issues, but here is a tutorial that explains the application of CSS Styles on Form Elements.
How do I get my footer to sit at the bottom…?
Need a div which makes space at the bottom of the main page (inside the #wrap div). Then, the footer (being inside #wrap) can be placed in that space by using absolute positioning. Like this :
CSS body, html {
height:100%;
}
body {
margin:0;
padding:0;
}
#wrap {
position:relative;
width:780px;
margin:auto; min-height:100%;
}
* html #wrap {
height:100%;
}
#clearfooter {
height:50px;
overflow:hidden;
}
#footer {
position:absolute;
bottom:0;
width:100%;
height:50px;
}
HTML

…content goes here… 

Can I attach more than one declaration to a selector?
Yes. If more than one declaration is attached to a selector they must appear in a semi colon separated list, e.g.;
Selector {declaration1; declaration2}
P {background: white; color: black}
Border around a table?
Try the following:
.tblboda {
border-width: 1px;
border-style: solid;
border-color: #CCCCCC;
}
/*color, thickness and style can be altered*/
You put this style declaration either in
an external stylesheet, or you can stuff it in
the section, like:
(here you can place your styles)
and apply it to the table as follows:

Content text and more content

That should give you a grey thin border around this table.
If you want the border to ‘shrink wrap’ around the table, then you have to use the tag instead the
tag. But that is not quite proper CSS or HTML, because a is for inline elements. A table is not an inline element, therefore the correct tag is a

. If you play around with it a bit then you have a good chance to achieve what you want and still have correct HTML/CSS.The other way would be that you apply the class .tblboda directly to the table (for IE and other contemporary browsers), like 
and you define another class for each stylesheet: .tblboda2In the NN4.xx stylesheet, you use the same properties as above, and in the IE and other contemporary browsers you carefully set all those properties to default, like {border-style: none;}
Then you wrap the table in the

with the class .tblboda2 (NN4.xx does that) (IE a.o.c.b. don’t do anything, because the border-style is set to “none” = no border at all).This way you have a table that is wrapped in a nice little border: .tblboda2 for NN4.xx, .tblboda for IE and other modern browsers. 
How do you target a certain browser?
IE can be targetted by preceding your properties with ‘* html’. For example…
#nav {
position:fixed;
}
* html #nav { /* this will target IE */
position:absolute;
}
Another way to target IE is with conditional comments. Put this (below) in the head – just before the closing tag – and put anything you want to be directed only at IE in another stylesheet.

If you need to target IE5x…
#wrap {
width:760px; /* for IE5x */
w\idth:780px; /* for all other major browsers */
}
How does inheritance work?
HTML documents are structured hierarchically. There is an ancestor, the top level element, the HTML element, from which all other elements (children) are descended. As in any other family also children of the HTML family can inherit their parents, e.g. color or size.
By letting the children inherit their parents a default style can be created for top level elements and their children. (Note: not all properties can be inherited). The inheritance starts at the oldest ancestor and is passed on to its children and then their children and the children’s children and so on.
Inherited style can be overridden by declaring specific style to child element. For example if the EM element is not to inherit its parent P then own style must be declared to it. For example:
BODY {font-size: 10pt}
All text will be displayed in a 10 point font
BODY {font-size: 10pt}
H1 {font-size: 14pt} or H1 {font-size: 180%}
All text except for the level 1 headings will be displayed in a 10 point font. H1 will be displayed in a 14 point font (or in a font that is 80% larger than the one set to BODY). If the element H1 contains other elements, e.g. EM then the EM element will also be displayed in a 14 point font (or 180%) it will inherit the property of the parent H1. If the EM element is to be displayed in some other font then own font properties must be declared to it, e.g.:
BODY {font-size: 10pt}
H1 {font-size: 14pt} or H1 {font-size: 180%}
EM {font-size: 15pt} or EM {font-size: 110%}
The EM element will be displayed in a 15 point font or will be 10% larger than H1. NOTE: EM is, in this example, inside H1 therefore will inherit H1’s properties and not Body’s.
The above declaration will display all EM elements in 15 point font or font that is 10% larger than font declared to the parent element. If this specific font is to apply to EM elements but only if they are inside H1 and not every occurrence of EM then EM must take a form of a contextual selector.
H1 EM {font-size: 15pt} or H1 EM {font-size: 110%}
In the example above EM is a contextual selector. It will be displayed in specified font only if it will be found in the context of H1.
Not all properties are inherited. One such property is background. However, since it’s initial value is transpar
What is the percentage value in ‘font-size’ relative to?
It is relative to the parent element’s font-size. For example, if the style sheet says:
H1 {font-size: 20pt;}
SUP {font-size: 80%;}
…then a inside an

will have a font-size of 80% times 20pt, or 16pt.What is wrong with font-family: “Verdana, Arial, Helvetica”?
The quotes. This is actually a list with a single item containing the well-known ‘Verdana, Arial, Helvetica’ font family. It is probably intended to be a list of three items. 
Unlike in most other CSS1 properties, values for the font-family are separated by a comma to indicate that they are alternatives. Font names containing whitespace should be quoted. If quoting is omitted, any whitespace characters before and after the font name are ignored and any sequence of whitespace characters inside the font name is converted to a single space.
So to ask for two fonts foo and bar the syntax is:
font-family: foo, bar
To ask for the two fonts Revival 555 and Iodine you can do this:
font-family: “Revival 555”, Iodine
You could also do this:
font-family: Revival 555, Iodine
which is equivalent. Notice that this is not three fonts; you can tell because after the “l” you didn’t hit a comma, (more list items to come) a semicolon (end of that property, another property coming up) or a curly brace (end of that rule). This is also equivalent:
font-family: Revival 555, Iodine
^^^^^^ whole bunch of spaces converts to one space
But this next one is asking for a different font with two spaces in the name
font-family: “Revival 555”, Iodine
^^two spaces, which are not converted
In general it is more tolerant of user typing to leave out the quotes. Sometimes you need them, for example there is a real font sold by Fontworks and designed in 1995 by Stephan M?ller called Friday, Saturday, Sunday. Yes, two commas in the actual font name. CSS1 can handle this:
font-family: “Friday, Saturday, Sunday”, cursive
Because it can handle this, the example in the title is syntactically correct. But what the author or tool wrote was almost certainly not what the document author intended.
How do I centre my page?
This is very easy. If we take the code in the last question and change it to this :
CSS
body, html {
height:100%;
}
body {
margin:0;
padding:0;
}
#wrap {
position:relative;
width:780px;
margin:auto; min-height:100%;
}
* html #wrap {
height:100%;
}
you get a page that fits an 800×600 resolution screen without a horizontal scrollbar, which will be centered at higher resolutions.
Must I quote property values?
Generally no. However, values containing white spaces, e.g. font-family names should be quoted as whitespaces surrounding the font name are ignored and whitespaces inside the font name are converted to a single space, thus font names made up of more than one word (e.g.) ‘Times New Roman’ are interpreted as three different names: Times, New and Roman.
Do any WYSIWYG editors support the creation of Style Sheets? Any text-based HTML editors?
As support for CSS in browsers has matured in the last year, both WYSIWYG and Text-based HTML editors have appeared that allow the creation or the assistance of creating Cascading Style Sheet syntax. There are now at least two dozen editors supporting CSS syntax in some form. The W3C maintains an up-to-date list of these WYSIWYG and text-based editors.
Which style specification method should be used? Why?
The answer to this one is tricky. The short answer is: “it depends.” The long answer is, however, another story.
If you are planning on using more than one style specification method in your document, you must also worry about Cascading Order of Style methods (see question 11.) If you are going to use only one method, then some guidelines about the nature of each method need to be kept in mind. The answer to this question is also very much related to the advantages and disadvantages to using each of them (next question.)
Method 1: External Style Sheets (The LINK [–>Index DOT Html] element)
This method should be used if you want to apply the same style to multiple documents. Each document can reference the stand-alone style sheet and use the styles contained within. Using this method, the appearance of many documents can be controlled using a single or small number of style sheets. This can save a LOT of time for an author.
Method 2: Embedded Style Sheets (The Style [–>Index DOT Html] element)
The syntax used with Method 2 is the same as that for Method 1. This method is a happy medium between External Style Sheets and Inline Styles (see below.). It should be used in place of Method 1 if you only want to specify styles for a single document. This method should also be used when you want to specify a style for multiple tag types at once or the list of style definitions is of larger size. Method 3: Inline Styles (STYLE attribute to HTML elements)
If you only have to apply style to one or a few elements in a single document, your best bet will often be an Inline Style. This method attaches a style definition within the HTML element it is modifying.
Justified Text?
You redefine the
tag like:
p {text-align: justify;}
and that renders all
s with justified text.
Another possibility is to define a class, like:
.just {text-align: justify;}
and then you style the paragraphs in question like:

 

Note that NN 4.xx has problems with the inheritance of styles; that some NN4.xx browsers have a funny way to interpret “justify”; and that you have to have at least one blank space between the last character and the
tag, because otherwise NN 4.xx likes to justify even a three word half-sentence… also, some browsers do a pretty ugly job of rendering justified text, adding spaces between words, instead of spaces between letters, as with word-processing programs.
Why can @import be at the top only?
A style sheet that is imported into another one has a lower ranking in the cascading order: the importing style sheet overrides the imported one. Programmers may recognize this as the same model as in Java, Modula, Object-Pascal, Oberon and other modular programming languages.
However, there is a competing model, well-known to C programmers, where the imported material is not lower in rank, but is expanded in-place and becomes an integral part of the importing document.
By allowing @import only at the top of the style sheet, people that think in terms of the second model (although in principle incorrect) will still get the expected results: as long as the @import is before any other overriding rules, the two models are equivalent.
Btw. In all the modular languages import statements are only allowed at the top. In C, the #include can be put elsewhere, but in practice everybody always puts it at the top. So there may not be that much need to allow @import elsewhere in the style sheet either.
Colored Horizontal Rule?
You can apply styles to Horizontal Rules


in IE without problems, but NN4.xx can only render the silvery HR. But there is a way around it:.rule {border-top-width: 1px;
border-top-style: solid;
border-color: #FF0000;
margin: 0px 2%;} 
that, applied to a div, should give you a red HR in NN4.xx and IE, with a 2% gap on the left and right side.
CSSharky Logo
On this page is an Example of a coloured ‘Horizontal Rule’.
Update:
Thanks to Matt Del Vecchio here is an improved format for the Horizontal Rule:
hr { height:0px;
border:0px;
border-top:1px solid #ff1493; }
….this works in both IE and Netscape. It tells the browser to not render the hr rule itself, and then sets a 1px border, which looks just how most folks want to render the hr rule. It uses the


element and that is better than writing your own class as all devices will know what to do with an 


tag.Do URL’s have quotes or not?
Double or single quotes in URLs are optional. The tree following examples are equally valid: 
BODY {background: url(pics/wave.png) blue}
BODY {background: url(“pics/wave.png”) blue}
BODY {background: url(‘pics/wave.png’) blue}
To what are partial URLs relative?
Partial URLs are relative to the source of the style sheet. The style sheet source can either be linked or embedded. To which source partial URLs are relative to depends on their occurrence.
If a partial URL occurs in a linked style sheet then it is relative to the linked style sheet. The URL of the linked style sheet is the URL of the directory where the sheet is kept.
If a partial URL occurs in an embedded style sheet then it is relative to the embedded style sheet. The URL of the embedded style sheet is the URL of the HTML document in which the sheet is embedded.
Note that Navigator 4.x treats partial URLs as being relative to the HTML document, regardless of the place where the partial URL occurs. This is a serious bug which forces most authors to use absolute URLs in their CSS.
What’s the difference between ‘class’ and ‘id’?
As a person, you may have an ID card – a passport, a driving license or whatever – which identifies you as a unique individual. It’s the same with CSS. If you want to apply style to one element use ‘id’ (e.g.

). In the stylesheet, you identify an ‘id’ with a ‘#’ ie. ‘#myid’…
As a person, if you are in a class, you are one of many. It’s the same with CSS. If you want to apply the same style to more than one element, use ‘class’ (e.g. 

). In the stylesheet, you identify a ‘class’ with a ‘.’ ie. ‘.myclass’…
If id’s are more restrictive than classes, then why not just litter your page with classes? Well, I think the main thing is that it’s simply wrong. You don’t put headings in ‘p’ tags – you use ‘h1’, ‘h2’, etc. You don’t (or shouldn’t) make a list by writing asterisks or the little divider bar ( | ) – you use list tags (‘ol’/’ul’ + ‘li’) . You don’t say that your footer is part of a class of elements called ‘footer’ – that’s just stupid – you can’t have more than one footer – it can’t be a class. Of course, practically, the effect is about the same – the rules are applied – but that’s not the point – it’s semantically wrong to do it that way… However, if you try to give more than one element the same id, you will have problems – so don’t do it.
An element may have an id and a class, but that’s usually not necessary. You can also give an element two classes if you need to – like this : class=”class1 class2″. It can be very useful. Needless to say, you can’t give an element two id’s.
Another difference is to do with power. You can give an element an id and a class, but if any of the properties of the two conflict, the id style will win. Ids are more powerful than classes.
One more useful thing about id’s is that they can be used as a link reference. Many people still think that you need named anchors to make links within a page, but that’s simply not true – in fact, the name attribute is deprecated in XHTML except for in forms. One example of using id’s as link references is this page. There are no named anchors on this page – the questions at the top of the page link to the id’s of the divs that the answers are in.I made a 10px-high div, but IE makes it 20px high…
Yeah
This problem sometimes comes up when you make a div just to contain the bottom border of a box, or something like that. In this situation, there’s no text in the div, but IE won’t let the height of the div be smaller than the line-height (which usually depends on the font-size). The answer is to set the font-size to zero.
CSS
#thediv {
font-size:0;

How do I place two paragraphs next to each other?
There are several ways to accomplish this effect, although each has its own benefits and drawbacks. We start with the simplest method of positioning two paragraphs next to each other.

Paragraph 1
Paragraph 2

Trickier is this example, which relies on positioning but does not suffer the vertical-overlap problems which plague many other positioning solutions. The problem is that it relies on an incorrect positioning implementation, and will break down dramatically in conformant browsers.


Paragraph 1

Paragraph 2

If floating is not sufficient to your purposes, or you cannot accept display variances in older browsers, then it may be best to fall back to table-based solutions.
Can you use someone else’s Style Sheet without permission?
This is a somewhat fuzzy issue. As with HTML tags, style sheet information is given using a special language syntax. Use of the language is not copyrighted, and the syntax itself does not convey any content – only rendering information.
It is not a great idea to reference an external style sheet on someone else’s server. Doing this is like referencing an in-line image from someone else’s server in your HTML document. This can end up overloading a server if too many pages all over the net reference the same item. It can’t hurt to contact the author of a style sheet, if known, to discuss using the style sheet, but this may not be possible. In any case, a local copy should be created and used instead of referencing a remote copy.
I want my page fonts to look the same everywhere as in?
a) Why are my font sizes different in different browsers ?
b) Why are my font sizes different on different platforms ?

These questions represent the tip of the iceberg of a large topic about which whole essays have been written and a wide range of different views are held.
The WWW was originally devised to present the same content in different presentation situations and for a wide range of readers: on that basis, “looking the same” is not a design criterion, indeed different presentations would be expected to look different.
Some would have it that this original aim is no longer relevant, and that the purpose of web design is now to factor out the differences between display situations and put the author in control of the details of the presentation. Others point out that CSS was designed to give the reader a substantial amount of joint control over this process, and that this is desirable, for example to accommodate users with different visual acuity.
Reading of textual matter on a computer screen is quite a delicate business, what with the relatively coarse pixel structure of a computer display; even with a close knowledge of the display details, it isn’t possible to achieve the detailed control that would be possible, say, on a printer. Whatever one’s aims, the practical truth is that many of the efforts made to guarantee the precise result on the screen have seriously counterproductive side effects in a www situation.
The CSS specifications themselves recommend that authors should not use absolute size units in a situation where the properties of the display are unknown. There’s a lot to be said for flexible design, that in an appropriate situation looks the way you had in mind, but still successfully conveys content and message in a wide range of other browsing situations.
And so, before looking at the technical detail of what can be specified, it’s strongly suggested that you read some of those essays on web design, and reach your own conclusions as to the strengths and weaknesses of the medium, and how you can best exploit the strengths in a web environment, without falling foul of the weaknesses.
When is auto different from 0 in margin properties?
In vertical margins, auto is always equal to 0. In horizontal margins, auto is only equal to 0 if the width property is also auto. Here are three examples, assume that there is a
that is a child of:
Example 1: auto value on the width.
BODY {width: 30em;}
P {width: auto; margin-left: auto; margin-right: auto;}
Since the width property is auto, the auto values of the two margins will be ignored. The result is a P that is 30em wide, with no margins.
Example 2: two auto margins
BODY {width: 30em;}
P {width: 20em; margin-left: auto; margin-right: auto;}
The P will be 20em wide and the remaining 10em will be divided between the two margins. Paragraphs will be indented 5em at both sides.
Example 3: one auto margin
BODY {width: 30em;}
P {width: 20em; margin-left: 2em; margin-right: auto;}
In this case, paragraphs are 20em wide and are indented 2em on the left side. Since the total width available is 30em, that means the right margin will be 8em.
Note that the default value of width is auto, so setting one or both margins to auto is only useful if you set the width to something other than auto at the same time.
How do I move the list bullet to the left/right?
CSS1 has no properties for setting margins or padding around the bullet of a list item and in most cases the position of the bullet is browser-dependent. This is especially true since most browsers disagreed on whether a bullet is found within the margin or padding of a list item.
In CSS2, properties were introduced to provide greater control over the placement of bullets (which CSS2 calls a “marker”) but these were not widely supported by mid-2001 browsers. Here is an example of changing a marker’s placement:
li:before {display: marker; marker-offset: 22px; content: url(triangle.jpg);}
In this example, a graphic of a triangle is inserted before the content of the li element, set to be a marker (through display: marker;), and given an offset of 22 pixels. Depending on the margin size of the list item, there may not be room for the marker to appear next to the list item’s content.
How does a simple CSS style rule look ?
P { font-family: serif; font-size: 1.2em; }
Here we see a rule with a ‘selector’ P that has been given two style declarations, i.e. two ‘property:value’ pairs.
‘font-family’ and ‘font-size’ are properties of the content of element P , and these properties are assigned the values of ‘serif’ and ‘1.2em’ respectively.
A colon ‘:’ is the value assignment symbol in CSS, so using an equal sign ‘=’ instead is an error and is required by the CSS specification to be ignored. Any browser that appears to honor this style is behaving improperly.
For length values a ‘unit’ is always needed and there shall never be any space between a number and its length unit.
A value given as e.g. ‘1.2 em’ is an error and is required by the CSS specification to be ignored. Any browser that appears to honor this style is behaving improperly.
A semicolon ‘;’ between declarations is required but it’s also good “rule of thumb” to put a ‘;’ even after the last declaration.
Finally, curly braces ‘{?}’ group one or more declarations into a final CSS rule.
Why are there gaps above and below my form in IE?
A lot of the time, when you find gaps that you can’t account for, they are due the default styles of different browsers – especially the margins and padding. IE gives forms some margins above and below forms while Firefox doesn’t. It’s like with lists – you’ll find bigger padding and margins for lists in IE than in Firefox. Paragraph margins are different, as are the margins on heading tags (h1,h2, etc).
A good way to not get caught out by these problems is to set all margins and padding to zero at the top of your style sheet and then add them as and when you feel the a need for them, in that way, any margins and padding will be the same in different browsers.
CSS
* {
margin:0;
padding:0;
}
If one were to set Text and Link colors using a style sheet, should one also define the background colors for these elements as well?
It is generally true that you should give background or background-color a value, but not necessarily a color value. E.g., if the document has a background image, you would “highlight” all links if you give them a background color.
body { background-image: url(light-texture.png) #FFF; color: #000 }
a:link, a:visited, a:active { color: #00F; background-color: transparent; }
By setting the background-image explicitly to transparent, you lower the risk of another rule in the cascade giving links a background that would highlight them.
How do you override the underlining of hyperlinks?
CSS has the ability to explicitly control the status of underlining for an element – even for hyperlinks. The correct way to do this in an external or document-level style sheet is:
A { text-decoration: none }
and within an anchor element as:
link text
Note: The underlining of hyperlinks is a long-standing visual convention that assists in the visual identification of active hyperlink areas. Many users expect to see hyperlinks underlined and may be confused and/or irritated if they are not used. User-defined style sheets address this user need by allowing the user to have final control over this feature. Unfortunately, wide support for this ability does not yet exist.
How do you show which page you’re on (in a menu)?
If PHP is not available to you, you could use the cascade. Put an id in your body tags and an id in each of your ‘a’ tags for the links.
Let’s say on page one you have this:
CSS
….
page one

In your CSS, you can have something like this:
CSS
#page1 a#page1link {
color:purple;
How can I specify two different sets of link colors?
By classifying each set of links and then attaching desired color to each set.
CSS:
You can name set1 and set2 any way you like as long as the names are made up of letters a-z, A-Z, digits 0-9, period, hyphen, escaped characters, Unicode characters 161-255, as well as any Unicode character as a numeric code.
Note: to avoid conflict with user’s settings a background property (background color) should also be specified together with the color property (foreground color).
How can I place multiple blocks next to each other?
In theory, the following will produce 4 “columns”:

Block 1
Block 2
Block 3
Block 4

Each “column” will occupy 25% of the screen. This relies on a correct implementation of float, which cannot be said of many legacy browsers. If you cannot accept display variances in older browsers, then it may be best to fall back to table-based solutions.
2. By making the block an inline element and then use text-align property

text

This technique depends on the incorrect implementation of text-align behavior in older browsers. It will likely cease to work in future CSS-conformant browsers, and eventually it will probably not be a viable solution.
Document Style Semantics and Specification Language (DSSSL)?
Document Style Semantics and Specification Language is an international standard, an expression language, a styling language for associating processing (formatting and transformation) with SGML documents, for example XML.
What is Extensible Stylesheet Language (XSL)?
XSL is a proposed styling language for formatting XML (eXtensible Markup Language) documents. The proposal was submitted to the W3C by Microsoft, Inso, and ArborText.
Which font names are available on all platforms ?
The simple answer is “None” which is why CSS offers five generic font names as ‘serif’, ‘sans-serif’, ‘cursive’, ‘fantasy’ and ‘monospace’. Never put any of these generic font names in quotes.
A CSS aware browser should make a suitable choice from the available fonts in response to each of those generic names.
Specifying any other font name in a www environment comes out as a suggestion only, that may or may not be acknowledged by a browser.
The problem with using names of specific fonts is that there is little point in naming fonts that few users will have, so you’re down to listing a few mass-market font names. This will then override any superior selection that a minority of discerning readers may have made for themselves.
Note also that fonts may differ in their character repertoire, but this is often not evident from the font name itself: by selecting an inappropriate font name, you might prevent internationalized content from displaying correctly for a proportion of users.
Why does Netscape lose my styles ?
Netscape 4.x has poor support for CSS. Having said that, the following points should be noted.
Invalid HTML will almost certainly cause Netscape to ignore your CSS suggestions at some point. You will find that valid HTML is your best friend, but for Netscape to work properly you must ensure that all elements in your markup which permit closing tags are explicitly closed.
Check and correct your CSS suggestions for the very same reason, Netscape 4.x is in fact doing “the right thing”, as per CSS specs (as opposed to MSIE) when it ignores style rules with errors.
Netscape 4.x has what’s called an “inheritance problem” into its TABLE element. It can be argued that NS is all within its right to behave as it does in this case, but since the workaround is quite simple it’s easy enough to just use it and be done with it.
Let’s say you want your TABLE content to “look the same” as your BODY content? “Redundant” styling comes to your help as in e.g. BODY, TABLE, TH, TD { /* insert your styles here */ }
On a generic level, Netscape 4.x likes to have style rules applied directly to the elements where they are needed. You can never really trust the inheritance principle to work correctly at any level in Netscape 4.x.
Why is it my ‘:hover’ declaration for links does not work ?
Assuming you have already checked that your style sheet declarations do conform to correct CSS syntax, it could be that you have overlooked the importance of a correct order of style declarations for links.
The CSS2 specification makes this following note on the importance of placing the dynamic pseudo-classes ‘:hover’ and ‘:active’ in correct positions in a list of style declarations.
Note that the ‘a:hover’ must be placed after the ‘a:link’ and ‘a:visited’ rules, since otherwise the cascading rules will hide the ‘color’ property of the ‘a:hover’ rule.
Similarly, because ‘a:active’ is placed after ‘a:hover’, the active color will apply when the user both activates and hovers over the ‘a’ element.