s of this moment, there is no browser that passes with 100%. This is normal with the acid tests, which typically make use of rendering technologies that no browser maker gets right. (It's pretty sad, too. The acid3 test uses nothing but standards developed in 2002 or earlier, which means that five years after the standards were released, not one single browser maker uses them correctly. That's lame, if you ask me!)
Internet Explorer 7 does dismally, with 12 out of 100 tests passed (and the rendering is screwed up beyond belief). Safari 3.1 is arguably the single most standards-compliant browser out there right now.
What's really lame is that Explorer does not even pass acid2, and does an incredibly dismal job of trying to render it. Acid2 came out in 2005, Internet Explorer 7 came out in 2006, and Internet Explorer does not pass acid2. It even fails acid1, which came out in 1998; it gets everything right in acid1 except that it underlines the hyperlinks, which it is not supposed to do.