Robert Biggs at CSS3 Wizardry:
Microsoft has been bombarding the media with claims about how much better IE9 is than all the other browsers, more HTML5 and CSS3 compliant than any other browser that ever existing and ever will. It’s the only browser that passes all the tests they made up. And, Microsoft has finally implemented the CSS3 selectors that were implemented by other browsers back in, what? 2003? Because Microsoft has updated IE to support CSS3 selectors and rounded corners, they want us to believe that somehow IE9 magically supports the whole slew of CSS3 visual styling. I’m afraid it doesn’t. As a matter of fact, IE9′s support for CSS3 visual styling is so poor that the results are shocking. Firefox, Chrome and Safari can render graphically rich interfaces using the sophisticated features of CSS3. IE9 does, well, rounded corners. That’s why I’m saying: IE9 is the IE6 of CSS3. Repeat that a few times until it sinks in because if you do Web development, you’re going to have to deal with it.
Be sure to see this comparison of rendering engines and how they handle CSS. Trident — the engine behind IE — is truly abysmal.