vincevincevince - 2:55 am on May 18, 2007 (gmt 0)
Just that thing is more than enough to force webserver to use xhtml while allowing browsers to render errors.
The philosophy to which you allude is then not a constraint upon the webmaster but upon the server. It implies that IIS, Apache, etc. should throw errors if you attempt to serve invalid HTML (and I actually agree that they should).