More on signatures on root…

If you have a file that contains the <?xml> processing instruction, IE is in tag soup quirks mode anyway, so for IE5 and up you lose nothing by hiding the extended DOCTYPE within the appropriate conditional comments. And IE3 people will already be seeing the <?xml>. But there's not a one-size fits-all solution for Firefox with the same data being served as application/xhtml+xml and as text/html, let alone other browsers.

Another nice idea, not quite ready for prime time. *sigh*