XHTML is the Most Important XML Vocabulary (O'Reilly)
Taking the long view of recent technology, XHTML may be the most important XML vocabulary ever created. What I mean is not that XHTML will be the most widely deployed XML vocabulary, though if we take the long view, it could be. What I mean is that XHTML puts XML's reputation -- and, by extension, the W3C's reputation -- on the line to a greater degree than any other XML vocabulary."
