Paschal L already mentioned article that describes how to add CSS2 intellisense support to VS 2003. As you might know, Whidbey introduces CSS-IE6, CSS1, CSS2 and CSS2.1 intellisense schemas. Original VS 2003 CSS schema is mostly about IE5. If you wish to retrofit CSS2 intellisense to VS 2003, you may have a look at schemas we ship in Whidbey. You will find them in C:\Program Files\Microsoft Visual Studio 2005\Common7\Packages\1033\Schemas\CSS along with the CSS.xsd that is used to validate CSS schemas on load. There is no guarantee that Whidbey schemas are directly compatible with VS 2003. I don’t know what happens if you copy Whidbey CSS2.xml over VS 2003 CSSMetaData.xml since we did make some changes in the CSS editor schema handling and intellisense code, but you probably can use Whidbey schema as a source of information. VS 2003 does not support switching CSS schemas so you can only use a single schema at a time. You will have to restart the VS 2003 when you want to switch between schemas.