Acid3 is a test page from the Web Standards Project that scores how well a rendering engine follows defined web standards, particularly DOM and JavaScript...
In March, both Safari's WebKit and Opera's Presto announced earning a 100% score in developer builds of their browser...
Actual shipping builds of the world's various web browsers haven't yet reached 100%. According to figures in Wikipedia, the latest Safari 3.1.2 has a score of 75, while Firefox 3.0.2 has reached 71, Opera 9.52 has reached 84, and Internet Explorer 7 is at 14.
Among mobile browsers, the shipping version of Safari in iPhone 2.1 reaches 74, while the Netfront browser hits 11, Opera Mobile reaches 2, Opera Mini has hit 79. Pocket Internet Explorer can't run the test due to a lack of JavaScript support.
Ref:
Apple Insider - WebKit becomes first browser engine to fully pass Acid3 test (Also see
Wikipedia - Acid3.)
<Insert sarcastic remark about commercial websites coded exclusively for IE>