“The update also makes Safari the first major browser to pass the Acid2 test. The probe verifies a browser’s compliance with several current internet standards. A quick probe by vnunet.com found that neither of the current versions of Firefox, Internet Explorer or Opera passed the test.”

http://www.vnunet.com/vnunet/news/2145215/apple-sharpens-tiger-teeth

http://docs.info.apple.com/article.html?artnum=301984