Re: Machine readable format for validation results

May I suggest a XML RPC or it's SOAP cousin for XHTML or XML documents?  That way you could explicitly validate with error return, or not as is your whim.

It should not be forgotten that the popularity of HTML and the web itself  rests upon the **loose** syntax of HTML and mass produced invalid documents.  You validate so you know you are doing it right, not because you have no 'right' to do it.