In Visual Studio 2013, CSS files that are included in your project/solution will now automatically be parsed and all HTML documents will gain CSS class intellisense.
ASPX and other WebForm files using the legacy editor do not benefit from this implementation in VS 2013, but may adopt the new system in future releases.
But you can still use this feature as follows:
- right click on the “default.aspx” file in the Solution Explorer
- “open with”
- select “HTML Editor”