If you use Firefox as your browser there's a handy extension that does this for you, and makes troubleshooting css problems a whole lot easier. (Wordpress.org)

This section covers some of the issues that can occur with your Mac, and provides all the troubleshooting steps you need to resolve an issue yourself. We also provide a lesson that tells you what you can do if your troubleshooting techniques aren't working. (Apple)

This troubleshooting guide is designed to be carried out in order. (Ubuntu)