Quoting the spec:
Conformance checkers must use the information given on the WHATWG Wiki ClassExtensions page to establish if a value not explicitly defined in this specification is defined, and if so, whether it is being used on the right elements.
This is problematic as previously conforming documents would be made non-conforming when a class name is registered and doesn't apply to all elements (then the previously conforming documents use it elements for which it doesn't apply according to the registration).
When an author uses a new class name not defined by either this specification or the Wiki page, conformance checkers may offer to add the value to the Wiki, with the details described above, with the "proposal" status.
It has been pointed out to me that the offers would drive developer crazy.
-- Henri Sivonen [EMAIL PROTECTED] http://hsivonen.iki.fi/
