Both Opera and WebKit have passed the Acid3 browser test. What is Acid3? It is a test page you can run that scores the browsers ability to render, pixel for pixel, a reference page. Acid3 not only tests CSS positioning and features, but also tests a browsers ability to manipulate and script DOM elements. Now if we could just get Firefox and Internet Explorer to pass, web developers would have a huge toolkit that would be cross-browser compatible without needing special hacks for specific browsers.