This will render a document into a standard Emacs buffer, applying as much of the stylesheet as possible (some things like proportional fonts may not be feasible in some versions of Emacs/XEmacs).

This would include a major mode for viewing the document and navigating the hyperlinks.

Bonus points for allowing manipulation of the document in various ways (turning on/off specific stylesheets, being able to view the DOM info of a specific point in the buffer, etc).