Simon Willison’s Weblog

There are two meanings to XHTML: technical and marketing. The technical kind (XHTML served using the application/xhtml xml MIME type) is a formulation of HTML as an XML vocabulary. The marketing kind (XHTML served using the text/html MIME type) is processed just like HTML by browsers but the authors attempt to observe slightly different syntax rules in order to make it seem that they are doing something newer and shinier compared to HTML.

— Henri Sivonen