Chapter 31. XHTML

While the HTML 4.01 specification goes a long way in tidying up HTML, it still suffers from sloppy artifacts of HTML’s fast and loose development. Over the years, little was done to make HTML perfectly SGML-compliant. As a result, we have a language with quirky features and browsers that easily forgive basic HTML coding errors.

With the creation of XML (see Chapter 30), the W3C finally had a standard set of rules for defining markup languages. It should come as no surprise that one of the first things they did with their shiny new set of rules is apply them HTML. The resulting XML-ized HTML standard is known as XHTML.

XHTML 1.0 is virtually the same as the HTML 4.01 standard, but more strict. The W3C is aiming eventually to replace HTML with XHTML to keep it in line with the larger family of XML-based markup languages.

This chapter reviews the differences and similarities between HTML 4.0 and XHTML.

XHTML Standards Development

Things are exciting over at the W3C. Now that they have XML on their toolbelts, they seem to be on a roll in rethinking and reshaping document markup. Between January 2000 and June 2001, they have turned out three XHTML Recommendations: XHTML 1.0, XHTML Basic, and XHTML 1.1 (XHTML 1.1 is still “Proposed” as of this writing, but since it’s on the verge of approval, I’ll count it anyway). This section looks at each one.


The XHTML 1.0 Recommendation (released in January 2000) is really just a reformulation of the HTML 4.01 specification ...

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