SitePoint has reported that IE8 has passed the Acid2 Test. As they explain, this test was developed “as a challenge to browser developers. In a single page, the test makes use of a broad range of features from several different web standards that developers have wanted to have in browsers for some time, and it uses them to display a deceptively simple smiley face.”
In short, passing the test means a browser meets web standards.
If IE8 has passed this test, this may mean the end of annoying hacks and workarounds to get sites to work in IE. An even more exciting result of this could be the end of CSS layouts made with floats etc., and the beginning of the ability to use CSS tables.