Firefox and Opera Fail the Acid2 Test
naylor83 writes "Four weeks ago, Opera's CTO Håkan Lie put forward the Acid2 challenge to the IE developers at Microsoft. The Web Standards Project has now silently published the promised browser test. Somewhat surprisingly, both Opera and Firefox fail to correctly render the test page. Obviously though, they're no where near as lousy as Internet Explorer. More screenshots are available at my blog, as well as at other people's."
Not even Firefox supports all of CSS2.
Google found an article that describes this in more detail
They deliberately made errors which the browsers should cope with according to the specs.