of the Internet. By migrating to XHTML today, content developers can enter the XML world with all of its attendant benefits, while remaining confident in their content's backward and future compatibility."

However, in 2005, the Web Hypertext Application Technology Working Group (WHATWG) formed, independently of the W3C, to work on advancing ordinary HTML not based on XHTML. The WHATWG eventually began working on a standard that supported both XML and non-XML serializations,