HTML is changing so fast it's almost impossible to keep up with developments. XHTML is HTML 4.0 rewritten in XML; it provides the precision of XML while retaining the flexibility of HTML. HTML & XHTML: The Definitive Guide, 4th Edition, brings it all together. It's the most comprehensive book available on HTML and XHTML today. It covers Netscape Navigator 6.0, Internet Explorer 5.0, HTML 4.01, XHTML 1.0, JavaScript, Style sheets, Layers, and all of the features supported by the popular web browsers.