Web Applications 1.0, more commonly referred to as X/HTML 5, is a new version of HTML that is vying to replace HTML 4 and XHTML 1. The X/HTML 5 specification is being developed by the Web Hypertext Application Technology Working Group (WHATWG).
X/HTML 5 introduces new elements to HTML for the first time since the last millennium. New structural elements include aside, figure, and section. New inline elements include time, meter, and progress. New embedding elements include video and audio. New interactive elements include details, datagrid, and command.
Recently, the beast came back to life. Three major browser vendors—Apple, Opera, and the Mozilla Foundation—came together as the Web Hypertext Application Technology Working Group (WhatWG) to develop an updated and upgraded version of classic HTML. More recently, the W3C took note of these developments and started its own next-generation HTML effort with many of the same members. Eventually, the two efforts will likely be merged. Although many details remain to be argued over, the outlines of the next version of HTML are becoming clear.
This new version of HTML—usually called HTML 5, although it also goes under the name Web Applications 1.0—would be instantly recognizable to a Web designer frozen in ice in 1999 and thawed today.