Web Standards Update for Microsoft Visual Studio 2010 SP1
http://visualstudiogallery.msdn.microsoft.com/a15c3ce9-f58f-42b7-8668-53f6cdc2cd83
Update June 3, 2012. Update to the latest CSS 3 schema even if you don't have Web Standards Update.
Web Standards Update provides the much wanted HTML5 & CSS3 support to Visual Studio 2010 SP1. It brings VS 2010 intellisense & validation as close to W3C specification as we could get via means of an extension. The most notable supported features by this extension are:
HTML5 – Video, Audio, Input Type, Drag & Drop, WAI-ARIA, Microdata, Schema.org
Browser API – GeoLocation & Local Storage
CSS3 – 2D Transforms, 3D Transforms, Animations, Background & Borders, Basic Box Model, Basic UI, Behavior, Color, Flexible Box Layout, Fonts, Paged Media, Hyperlink Presentation, Line, Lists, Marquee, Media Queries, Multi Column, Namespaces, Presentation Levels, Ruby, Selectors, Speech, Syntax, Template Layout, Text & Transitions. It also supports vendor specific prefixes like –ms, -webkit & -moz.
Note: This extension is created by a bunch of folks within Microsoft in their spare time. This is NOT an official Microsoft product