Visual Studio 2010 now supports HTML5.0 and CSS3
"We just released the first Web Standards Update for Visual Studio 2010 SP1. Despite its name, the update also works for Visual Web Developer Express 2010 SP1. You can read more on our team blog.
In this first release of the update, we have focused on bringing the HTML5 support up-to-date, adding CSS 3 support and bring more new API’s to the JavaScript intellisense. The plan is to make a release about every 3 months to keep Visual Studio updated with the changes made by W3C." Microsoft team member announced today.
Using Web Standards Update for Microsoft Visual Studio 2010 SP1 which is free extension you can know develope your webpages over HTML5 and CSS3 and enjoy it's wondeful features based on current W3C specifications.
You can download it from Here