I'm installing Visual Studio 2010 service pack 1 at the minute. Among the promises of stronger, faster, better statements on the blurb is the claim that SP1 supports HTML5 and CSS3 intellisense. Not all HTML5 elements are supported though, and you ahve to explicitly turn it on after installing the update. Also, CSS3 support is not complete. Hopefully, this will be addresses in SP2 due towards the end of the year.