<p>This specification defines <abbr title="Extensible Hypertext Markup
Language">XHTML</abbr> 1.0, a reformulation of HTML
4.0 as an XML 1.0 application, and three <abbr title="Document Type
Definition">DTDs</abbr> corresponding to
the ones defined by HTML 4.0. The semantics of the elements and
their attributes are defined in the W3C Recommendation for HTML
4.0. These semantics provide the foundation for future
extensibility of XHTML. Compatibility with existing HTML user
agents is possible by following a s