I'm late to the party, but Opera has decided to stop strict parsing of XHTML (via Sam Ruby):

[...] we've decided to stop throwing draconian XML parsing failed error messages [on invalid XHTML], and instead, attempt to reparse the document automatically as HTML.

I have long said that draconian XHTML error handling is an unstable equilibrium and it would only last as long as all of the browser vendors didn't blink. Well, Opera has blinked; they've picked the user friendly alternative over the strictly standards compliant one (or semi-strict, since they apparently already offered an option to reinterpret the page as HTML, unlike eg Firefox). It now remains to be seen how long it will be before other browser vendors do the same thing.

(I expect Firefox to be the last holdout because Firefox people are in some ways very user hostile in the name of doing 'the right thing'.)

While this Opera blog entry was about a development snapshot, the announcement for Opera 11.60 mentions this as a feature of 11.60. So this is now out there in the wild in a general release browser.

(Now I'm wondering if someone has or could make Firefox extension to do the same thing.)