Check your CSS code without leaving the IDE by using CssCop, which brings the CSS Lint functionality to the Visual Studio environment.

I hope some one has seen this behavior before, because I am stumped.Whenever I try to open any CSS file all I get is: This operation could not be completed ...

It's easy to miss that you've opened a read-only file in Visual Studio: When you open a file you can't change, a tiny little lock icon appears on the tab of the editor window to the right of the ...