The developer is able to use a great range of hacks that assure the compatibility between the browser standards and the used standards. Also, the @import statement allows the developer to hide the more advanced styles from older browsers, such as Netscape 4.x. But its great disadvantage is the usage of an additional HTTP request in the HEAD section of the document, which is very sensitive to the browser performance.

Basically, there are two techniques that allow the developer change the style of the site according to the type of browser: conditional CSS and conditional SSI. Conditional CSS I a method that allows the developer to include additional CSS styles for browsers, without interacting with the older ones at the expense of additional HTTP requests. On the other hand conditional SSI and the combination of external CSS with JavaScript allows you to use less HTTP requests per page.

Using the CSS hacks is much more complicated in XHTML documents, as they are done in XML. So, they are working with different notions concerning comments and special characters like < and &. Also, some XML parsers tend to totally erase the comments when parsing, so the classic ways of commenting the CSS code in comments in order to hide it from older browsers is not consistently working with XHTML

The conditional server-side includes is a great tool for delivering customized content to browsers and platforms that use different standards. Also, with conditional CSS you can add more CSS rules for the newest browsers without conflicting with the rules set with the older ones. It offers a better alternative for the @import statement and the common used CSS hacks used today, by using less HTTP requests to handle the webpage.

All the tags that are contained in a version of HTML are defined in its DTD, so the DTDs are like some dictionaries of all the possible tags in the markup language. It contains not only the HTML tags, but also what do they mean and how they are related one to another.

Practically, there are two types of DTD declarations: an internal and an external subset of tags. They are both optional. The declarations contained in the internal subset form are the DTD declarations included in the document itself. The external DTD declarations can be referenced in two way: by a public identifier and by using a system identifier.

The problem with the external DTD subsets is that a document using them may be only partially parsed and cannot be fully validated by the validating SGML or XML parsers working in the standalone mode (meaning that the parsers will not attempt to get the external entities  so that their text will be inaccessible).

There are several types of public DTDs, among which the most popular are:

1. Strict HTML 4.01
2. Transitional HTML 4.01
3. Strict XHTML 1.0
4. Transitional XHTML 1.0
5. And other different types.

It is possible for everyone to create his own type of DTD declaration, by creating a file which corresponds to certain rules. A DTD document must contain element type declarations, attribute list declarations, entity declarations and notation declarations.

DTDs proved to be a flexible instrument for the usage of developers, so that they can extend and modify the range of tag definitions and also create new types.

In time, when the standards became more important, the developers had to choose whether to create the next version of browser closer to the W3C standards, but disable support for the older sites, or creating it conforming to the internal standards, but which would preserve the quality of the sites created specifically for this browser. So the creation of standard-complying browsers would bring problems. But on the other hand, remaining on the old standards would create a state of confusion, similar to the Browser Wars Era.

In such a way, it was decided that every browser would be able to work in two modes: quirks mode, that represents the old standards supported by the browser, and strict mode which fully complies with the W3C standards. IE Mac was the first browser to support these modes, but other browsers like IE Windows 6, Mozilla, Safari and Opera also started the support of these modes. IE5 and older browsers, such as Netscape 4 are permanently working in quirks mode.

Now another problem appears: how does the browser choose to work in strict mode or in quirks mode. The problem was solved through “doctype switching”. Any HTML and XHTML documents, according to the standards, must contain a doctype, which tells to the browser which flavour of (X)HTML it is being used on the page. As the older pages do not contain a doctype, its absence triggers the quirks mode. On the other side, the majority of doctypes triggers the browser in strict mode. Any browser has its own list of doctypes and in such a way, basing on the doctype information, it can switch itself from quirks mode to strict mode and vice versa.

TIDY can correct the mismatched tags, correct the tags put in the wrong order, and it can perfect the lists that miss some required tags. It practically reduces to zero the work needed to be done by the coder on correcting errors.

This utility is famous for being able to fix a great range of problems, and also bring to your attention the errors it doesn’t know how to solve by itself. TIDY will show you what error is unable to solve, with the line and column numbering the code. The other problems it is able to solve by itself will be shown as warnings.

Now, Dave Ragget no longer works on this project, it is being continued by a group of volunteers on the Source Forge community. The source code remains open under an open source license, and if you found some problems or bug, or you have some enhancements requests, or wrote some patches.

Another way TIDY s known to make miracles is editing the HTML produces from WYSIWYG HTML editors. It changes radically the code received from Word 2000 and even from Word 1997, is you use the “Word-2000” config option.

TIDY was made for Linux, so it was created according to the UNIX philosophy: a program should do one thing, but should do it good. Even though it has no GUI and you have to read the manuals in order to be able to use it and know all the available options, it does its own job excellently.

Also, HTML TIDY will not only clean a great range of errors, it can also show you the places you must work by yourself, because if there are errors that the program does not know how to fix, it will show you an error message and you will have to fix the code by yourself.

Dave Ragget no longer works on this soft, so it is now being maintained by a group of volunteers at the Source Forge. In order to be able to use HTML Tidy, you have to just download the latest version from any famous site and unzip it on your PC. After that, you will need to modify the AUTOEXEC.BAT file that comes with windows, in order to be able to launch the executable tidy.exe without specifying the full path to it. Or you could just unzip it in a directory specified in that file.

After that, just run the Windows Command Prompt and write the command “tidy <name of the file>”. It should parse the entire file and find all the errors it has. If you need additional options, you could try the command “tidy -help”, which will write on the screen all the options available with the program. Also, you could use the GUITIDY program, which is simply a graphical interface on top of the command-line program.

A Store is an important part of the tools Amazon offers to people that are in its associates program. So, now every user of aStore is able to change the CSS interface of the look of his site, having the opportunity to change over 8000 characters of the CSS code for page, such as the product description and search results. New themes for aStore can be created, and also the members would have the opportunity to share them among themselves.But there is a great minus in the HTML markup of the pages, which would limit the possibility of customization. It is simply a strange set of DIV and TABLE tags, which do not offer a lot of semantic information. Also it is not a valid HTML, because it has no DOCTYPE, and other problems like unencoded ampersands. Because the page has no DOCTYPE, it is being rendered into Quirks Mode, which is very important if you plan to customize an aStore.

We could say that this kind of approach is almost revolutionary for such a major corporation as Amazon. Instead of relying on some scripts, that provide the end-user with a set of font-pickers and color-pickers, they give to the user a great part of the control over the site. Of course, the font and color pickers are also a good option, but the choice of giving control over CSS to the associates increases the interactivity and creativity of the site, on the other hand requiring the knowledge of CSS. The font and color pickers of course do not require additional knowledge of CSS, but by using them one cannot get such complex changes.

In the end, it only depends on your choices and knowledge, whether you like CSS or prefer simpler ways to change the image of a site.

As a good example one can use the HTML code. If you use in the e-mails you send incorrect or outdated code, domains such as Hotmail and AOL would surely block it, either send to bulk or junk folders. Even if you see that your email has rendered correctly, and looks just fine to you, Pivotal Veracity, a delivery-monitoring service provider, estimates that nearly every message sent in HTML doesn’t fully comply with the World Wide Web Consortium standards.

Every ISP manipulates differently the e-mails it receives, and therefore the messages that are passed at one destination can be easily blocked at another ISP. Because very many spam mails are sent in HTML format, with heavy use of HTML syntax and formatting errors, in order to trick some of the ISPs, many spam filters will simply delete or send to bulk all the messages that do not correspond to the W3C standards. Well, some infractions are minor and will allow the passage of the mail. An example of such an infraction could be the omission of the tag “alt”, which describes the content in an image tag. Many other faults can send your e-mail the bulk folder.

Pivotal Veracity recently tested a great number of HTML email messages in order to see if they were accepted or rejected by the most popular ISPs. Here are the results if the tests:

• If you use a tracking beacon below the closing HTML tag, your e-mail will be filtered and sent to bulk folder on MSN/Hotmail
• A badly constructed boundary between the text and HTML portions of a multipart e-mail message will send your e-mail at the bulk folder in MSN/Hotmail
• Using hex-encoded characters in URLs (for example by substituting the “%20” code for a space with its hex equivalent) may get the e-mail blocked or into the bulk folder at AOL, CompuServe and MSN/Hotmail.
• Usage of a decoy link that shows one URL in the e-mail but actually redirects you to another URL when clicked will also get the e-mails rejected or sent into the bulk folder at MSN/Hotmail

Anyway, there are great differences between these languages. XSLT was thought of like of a style sheet language, whose primary purpose was to render on screen the XML code, for the commodity of the human eye. XQuery was conceived more like a database query language, similar to SQL. Therefore, XSLT is better handling the documents with more flexible structure, while XQuery better manipulates the relational joints in database.

As usability studies have shown, the XQuery language is easier to learn, especially for people that have previous experience of SQL and other database languages. XQuery is a smaller language, able to create more concise programs. In contrast to XQuery, an orthogonal language, XSLT is more flexible, being a two-language system in which XPath expressions can be nested in XSLT expressions, but not vice-versa. Another strong point of XSLT is that it allows making small changes to a document, by using a coding pattern that involves an identity template, which copies and modifies the selected nodes on the fly. XQuery has no equivalent pattern, but it can appear in the following versions. Another facility that cannot be found in XQuery is any mechanism of polymorphism. The absence of this capability starts to be felt when writing larger programs, or when writing code meant to be reusable in different environments. In this area, XSLT offers the possibility to dynamically match template rules and to override rules using xml:import, that make it possible to write applications with multiple customization layers. The absence of such features in XQuery make it very amenable to static analysis, and also it becomes easier to detect errors in the XQuery code at compile-time.

XSLT 2.0 uses XML syntax, which makes it rather verbose in comparison to XQuery 1.0. Many applications take advantage of this, by using XSLT to read, write and modify style sheets dynamically as a part of a processing pipeline. By contrast, the XQuery code is more suitable for embedding with traditional programming languages, like Java or C#. If necessary, XQuery can be expressed in XML code, which is called XQqueryX. It is very verbose and hard to understand but can be easily processed for example with XSLT style sheets.

XHTML is not much different than HTML version 4.01. If you are aware of coding in 4.01 version then you can use the similar coding style in XHTML as well. Starting with this version could be good for developers. You can follow the coding system with lowercase letters and not at all miss ending tags. This ending tags will look like </p>.

Mentioned below HTML 4.01 standard reference could be a great help for them.

Before we start doing coding some basic differences are required to learn about XHTML and HTML.

1. XHTML elements are important and should be properly nested.
2. These elements should be closed always once the coding is complete.
3. You have to use the elements in lowercase.
4. There should have at least one root element.

Tags used in both languages having little difference like if you use the tags of HTML you can apply <b><i>Bold the letter with italic</b></i> where in XHTML you have to enter <b><i> Bold the letter with italic</i></b> way.

In HTML you can place the codes anywhere inside the <html></html> tags, but closing with the tags is not compulsory. However, this condition changes in XHTML and if you are using any code in it you have to close it in proper way.

A new feature is being launched of Microsoft® Internet Explorer 4.0 (IE 4.0) and that is Data binding. It allows developers to make websites that are faster to access, those which are more interactive, simplest to developer, and that needless server sources. These become possible by using the D-HTML support developed into IE 4.0.

D-HTML or dynamic HTML enables all the essential settings on a Web page to be controlled throughout scripting or editing languages. Data binding always prefer D-HTML in combination with easy declarative language rules to present the content using normal HTML basics with no options to difficult scripting. As a substitute of the customary way of integration of data from the HTML all through server side patterns or CGI scripts prior to it is sent to the browsing tool, data binding executes this process on the client side once the a page is established.

This binding fluctuates from fixed data publishing tactics. It uses normal HTML language as a pattern for the information and combines the data from the model asynchronously as the information is broadcasted to the client like representation of a GIF in spite of creating the complete webpage on server. The results in webpage that shows the data in increasing way as it’s broadcasted to the client for sooner early reply time also lets the developers to develop webpage’s.