HTML

HTML Comes of Age: XHTML

You know your HTML and you've got the hang of XML. Why not try XHTML. John will go through how to use Extensible HTML and its benefits.

Author Info:

By: Don Kiely

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March 03, 2003

TABLE OF CONTENTS:

· HTML Comes of Age: XHTML
· Two Great Tastes that Taste Great Together
· Extensible HTML
· XHTML Syntax
· Rocky Upgrade Path
· Moving to XHTML
· Roping the Wild, Wild Web

Despite the best efforts of the W3C, HTML has evolved in a less than orderly fashion. Because HTML is itself not extensible, browser vendors have rather haphazardly added tags. HTML has evolved at a pace far greater than any standards body could possibly keep pace with, so that the HTML standard is mostly a codification of existing practice rather than a source of innovation itself. As a result, any given HTML authoring tool supports at best a snapshot of HTML tags at a given time, no matter how fast the author runs to keep up.

Unfortunately, that means that your favorite HTML editor today may not be your tool of choice tomorrow, when XHTML becomes the norm. Unless, of course, Windows Notepad is still your editor of choice; then you're in fine shape to write new code. XHTML is too new for any of the major players to have made any commitment to support it. But with the rapid spread of support for XML, I'd be rather surprised if all of the major editors didn't rush to implement support.

During the transition to XHTML, validating code will be one of the biggest challenges. Validation is a process that verifies documents against the associated DTD, checking to make sure that the structure, elements, and attributes are consistent with the definitions in the DTD. Validating an XHTML 1.0 document involves verifying its markup against one of the three XHTML DTDs.

The W3C has an HTML Validation Service that is based on an SGML parser, with options such as including Weblint results and displaying the parse tree. The good news is that when the HTML Compatibility Guidelines are followed, XHTML 1.0 documents can be rendered on HTML 4.0-compliant browsers. One way to use the W3C validator is to place a link to http://validator.w3.org/check/referrer on your Web page. Clicking the link with your page loaded validates your page.

XHTML 1.1 is already under development, and will serve to make this next stage of Web technologies even more flexible. XML and HTML have a lot to offer each other. XML is not the "HTML-killer" it was touted in its early days, but when teamed up with its alleged victim, it promises to take over the Web.

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