HTML5
HTML5 is the latest version of HTML and XHTML. The HTML standard defines a single language that can be written in HTML and XML. It attempts to solve issues found in previous iterations of HTML and addresses the needs of Web Applications, an area previously not adequately covered by HTML.
HTML5 defines the fifth major revision of the core language of the World Wide Web, HTML. "HTML5 differences from HTML4" describes the differences between HTML4 and HTML5 and provides some of the rationale for the changes.
courtesy of HTML.ORG and more informations

