I'll think of a good title later

I'm curious about this Acid 2 test. For those that don't know the Acid2 test is a fairly advanced webpage created by the Web Standards Project using a variety of existing standards. All the top browser people (& possibly Microsoft as well) are busy beavering away on in a race to be the first to render it correctly.

My question is: Exactly which browser did the W3C use to test that their testcase is working correctly?

The Safari team have recently announced that they are the first to correctly render the test case, but Opera's approach to the problem (that is to add the Acid2 features while making sure that they don't break anything else in the process) sounds far more sensible.