What is HTML and XHTML?

HTML = Hypertext Mark-up Language.
XHTML = eXtensible Hypertext Mark-up Language.

Since the HTML mark-up language was first created in 1991, the World Wide Web has expanded and evolved far more than was ever envisaged by its creator, Tim Berners-Lee. Website designers have pushed HTML to its limits and beyond, and even though the language was extended three times, it soon became apparent that a more flexible and robust mark-up language was called for. The new standard needed to allow for semantic instead of just presentational mark-up; to enforce stricter discipline in its deployment; and to enable developers to work more efficiently with the vast amounts of data that modern websites and web applications are required to handle.

Thus in 1998, the World Wide Web Consortium (W3C) came up with XML: an efficient new language with far greater power and flexibility than HTML. The following year the W3C set about recreating HTML as an XML application and thus in 2000 they released XHTML into the wild.

Five years later and Microsoft have still not enabled Internet Explorer to parse XHTML files in the correct manner, so Explorer handles the code as if it were HTML, but the web developer community is hopeful that Microsoft will get their act together soon! In the meantime, by preparing websites in XHTML now, they work on older browsers yet we are ensuring that they will still be functioning correctly in many years to come.