Thanks for your extensive answer, Shannon.

I agree with your findings (form tags name/id attribute, script tag
language/type attribute). Additionaly, .NET is keen on creating id tags
beginning with (or containing) an underscore, which is also a no-no in XHTML. 

Oh well, here's hoping for a service pack in the near future, all a bit of
an embarrassment for MS, really.

Best

Hadj Ullelah