Extensible Hypertext Mark-up Language (XHTML) was created to be a synthesis between Hypertext Mark-up Language (HTML) and Extensible Mark-up Language (XML), but Microsoft never implemented support for XHTML in their Internet Explorer browser so any advantages it could have brought - such as XML namespaces MathML or SVG - were never realised.

The differences between the two are mainly one of syntax with XHTML being case-sensitive and requiring rigid closing with an end tag. Internet Explorer handles XHTML by using its inbuilt parser to read the language the same as it does HTML.

The reason that XHTML is so much more popular than its HTML cousin amongst the web design community is that many are still sold on what XHTML originally promised and the fact that the world governing standards body, the W3C, announced that HTML would no longer be developed after version 4.01 Strict.

In 2002 the W3C commenced work on XHTML 2, but within a few years the world's browser makers conspired together to commence work on a new version of HTML. They considered that XHTML 2 was too specific to the presentation of data and not universal enough for all website needs.

In 2008 the W3C heeded their call and formally announced the roadmap for HTML 5.

For a while it looked like the rather gigantic differences between HTML 5 and XHTML 2 would eventually give webmasters genuine choice rather than the false hope of HTML 4 and XHTML 1, but in the spring of 2009 the W3C publicly declared they were winding down all work on XHTML 2 in order to concentrate time and resources on HTML 5.

For those webmasters who prefer to code in XHTML it may seem that the W3C has consigned their choice to the dustbin of history, but fear not: XHTML will live on! Let me explain.

The reason XHTML 2 failed was that it was too adventurous. It was not backwards compatible with either version 1.0 or 1.1 and in effect tried to reinvent the wheel; but the unique syntax of the XHTML 1.0 and 1.1 will live on in XHTML 5, a variant of HTML 5.

Briefly, some new features of HTML 5 are new elements - section, article, footer, audio, video, progress, nav, meter, time, aside, canvas, datagrid; new types of form controls - dates and times, email, url, search; and deprecated elements dropped - center, font, strike.

Due to some major differences between the consulted parties on key aspects of HTML 5, it is not expected to be finalised for at least 10 years, although the recent W3C announcement that they will throw their full weight behind version 5 instead of XHTML 2 may shorten this time frame.

Elements of HTML 5 are have already appeared in all major browsers, including Internet Explorer 8.

So fear not hard-working web designer - XHTML will continue to be with us for years, if not decades to come.