CSS Scanner
CSS Scanner helps you clean and tidy up your css/stylesheet
...It then lists you those CSS selectors and classes that are not used or not defined and those which are used.
This way it helps you get an overview of your CSS/stylesheet definitions and lets you easily clean them up.
There's a precompiled .msi installer for Windows avaliable for download. Just install and find CSS Scanner in your start menu folder "CSS Scanner".
Click on the info icons of the GUI if you need help.