Code name Wilbur, for HTML 3.2 is start of HTML at W3C, which was followed a few years later by HTML 4.0, then HTML 4.01. HTML 4.01 and now HTML 5 is the last version of HTML, and is also the final W3C specification to define the semantics of markup. From HTML 3.2 to HTML 4.01, the language has improved a great deal, focusing on such issues as:

• Separation of presentation from structure
• Improved accessibility features
• Improve internationalization features
• Improved document rendering

XHTML 1.0 was created shortly after HTML 4.01 to help the transition of hypertext to a new generation of mark-up languages for text. XHTML 1.1 is an additional step toward a more flexible version of hypertext with the full benefits of XML architecture and integration of different technologies. Note that XHTML 1.1 has slighly improved the semantics of HTML 4.01 by including the Ruby module, used in particular languages like Japanese scripts (read the Ruby Specification for more information). For practical purposes, the discussion here will focus on HTML 4.01 and XHTML 1.0.

The semantics

When we refer to the “semantics” of a language, we’re referring to the meaning of a given tag. HTML 4.01 and XHTML 1.0 assign the same semantics to their elements and attributes. Lets have an example, an element address has exactly the same meaning in HTML 4.01 and XHTML 1.0: they’re both used to mark up addresses. (Clarification: address is used to mark up contact information for a document.) Only bits of the syntax varies between the two languages. For example :

HTML 4.01 example

<img alt="web design for psd2xhtml"

   src="/images/design_psd2xhtml.jpg">

<p lang="fr">Je

levai la tête pour regarder les

étoiles.  Leur vue apaisa peu

à peu les battements de mon

coeur.</p>

<p><cite>Chroniques

de l'oiseau à ressort</cite>

 - <cite>Haruki

 Murakami</cite></p>

XHTML 1.0 example

<img alt="web design for psd2xhtml"

   src="/images/design_psd2xhtml.jpg" />

<p xml:lang="fr">Je

levai la tête pour regarder les

 étoiles. Leur vue apaisa peu

 à peu les battements de mon

 coeur.</p>

<p><cite>Chroniques

de l'oiseau à ressort</cite>

 - <cite>Haruki

 Murakami</cite></p>

There are only few differences between the syntax, They are still very similar.

Both languages come in three flavors: Frameset, Transitional and Strict. The “strict” version is strongly recommended by the W3C for regular documents. Using strict versions removes problematic elements as well as forcing a significant separation between the structure of your document and its presentation. Transitional versions allow deprecated elements to assist those implementers to upgrade smoothly their software or their content.

Using the right tool for the job

Is there any advantage to using HTML 4.01 over XHTML 1.0? There is no simple answer and the benefits you will gain are tied to how you’re using the language in a given situation.

Switching from HTML 4.01 to XHTML 1.0 brings almost no direct benefits for the visitors of your Web site; still, there are several good reasons for Web authors to make the switch:

XHTML is easier to maintain

XML syntax rules are far more rigorous than HTML. As a result, XHTML makes authors work more precisely, having to address issues such as:

• all elements and attribute names must appear in lower case
• all attribute values must be quoted
• non-Empty Elements require a closing tag
• empty elements are terminated using a space and a trailing slash
• no attribute minimization is allowed
• in strict XHTML, all inline elements must be contained in a block element

In HTML, case, quotes, termination of many elements and uncontained elements are allowed and commonplace. The margin for errors in HTML is much broader than in XHTML, where the rules are very clear. As a result, XHTML is easier to author and to maintain, since the structure is more apparent and problem syntax is easier to spot.

XHTML is XSL ready

As you are probably aware by now, XHTML 1.0 is the reformulation of HTML 4.01 in XML. Therefore, XHTML documents are hypertext documents and XML documents. A powerful technology has been developed at W3C to manipulate and transform XML documents: the Extensible Style sheet Language Transformations (XSLT). This technology is tremendously useful to create various new resources automatically from an XHTML document. For example

• You can create a table of contents for a long document
• Get a quick overview of a page by listing its languages and structural outlines! See the Semantics extractor for this page, created by W3C QA Working Group member Dominique Hazaël-Massieux
• You can provide a printable version of your documents by using the XSL-FO features of XSL
• You can produce an RSS feed directly from your page, check out the QA RSS feed to see this in action

XHTML is easier to teach and to learn

The syntax rules defined by XML are far more consistent than those found in HTML and therefore easier to explain than the SGML rules on which HTML is based.

XHTML is ready for the future

When the new version of XHTML becomes a recommendation, XHTML 1.0 documents will be easily upgradable to this new version, to allow to take advantages of its exciting new features. It’s likely that an XSLT style sheet will be available by then to help you move your XHTML 1.0 (strict) documents to XHTML 2.0 documents.