CSSCop makes it easy to adhere to best practices for writing stylesheets. It catches common errors that affect browser compatibility and much more. You can think of it as FxCop for stylesheets.
To run CSSCop, simply right-click any CSS file, folder or project in Solution Explorer. That kicks of the rules engine and a list of warnings is added to the Error List.
The first time CSSCop is running, it will create a settings file (csslint.xml) in the root of your website. You can modify this file to turn rules on and off as you see fit. You can also specify whether or not the warnings should be treated as errors and be shown as such in the Error List.