HTML and CSS Reference
However, HTML version 4.01 is not XML compliant. Hence, the W3C of-
fers XHTML, a reformulation of HTML that is compliant with XML. XHTML
attempts to support every last nit and feature of HTML 4.01 using the
more rigid rules of XML. It generally succeeds, but it has enough differ-
ences to make life difficult for the standards-conscious HTML author.