(Thread moved to www-html@w3.org at danc's request.)

Ed Rice <ed.rice@hp.com> wrote, on w3c-html-cg@w3.org:
>
> Doesn't including the non-well-formed/invalid documents in the
> architecture/design actually validate the design and say that there is
> no such thing as a non-well-formed document?

No; you can simultaneously say that something is invalid and say exactly
how it should be processed. CSS does this; for instance:

    p { color: "red"; color: green; }

...is completely invalid CSS (you can't pass a string to the property
'color'), but every conforming UA will handle it the same.

In the case of HTML5, the HTML5 parser spec:

    http://whatwg.org/specs/web-apps/current-work/#parser 

...defines what is an error (non-conforming syntax) and what isn't.

HTH,
-- 
Ian Hickson