Validating CSS online

I recently had a problem with a webapp where things were showing up but I could not figure out why. The CSS seemed correct at a glance but someone else had written it so I was not very familiar with it. After struggling for awhile I did the smart thing and asked Gonzalo Silverio if he had any ideas (which of course, he did). He pointed me to this awesome CSS validator at http://jigsaw.w3.org/css-validator/. You can upload a css file or simply provide a URL to the file and it will give you a nice little report that tells you what is wrong.
A similar service for validating your markup is available at http://validator.w3.org/.