CSS 3.0 in Visual Studio 2010
Microsoft developers have released an update to the web standards to include CSS 3.0 in Visual Studio.
Web Standards Update for Microsoft Visual Studio 2010 SP1 http://visualstudiogallery.msdn.microsoft.com/a15c3ce9-f58f-42b7-8668-53f6cdc2cd83
After a simple installation, you will have the CSS 3.0 option in Visual Studio.
(The toolbar command is called "Cascading Style Sheet Version for Validation", and is on the "Style Sheet" toolbar.)
If you don't want to wait for the service pack, check this out:
http://visualstudiogallery.msdn.microsoft.com/7211bcac-091b-4a32-be2d-e797be0db210/view/Discussions
Worked great for me, although I needed to consult the Q & A for some installation tips.