Defines a single namespace for html:
Relies on HTML 4.01 for the semantics and data types of elements and attributes
Defines XHML 1.0 DTDs corresponding to HTML4's strict, transitional and framset DTDs
Provides guidelines for authoring XHTML documents for delivery to existing Web browsers
Existing HTML can be trivially converted to XHTML using W3C's Open Source HTML Tidy utility