Compressing CSS is a great way to save some bandwidth, especially on more complex sites with stylesheets reaching more than 1000 lines of code. There are many websites out there that will compress your stylesheets for you, but the problem is maintaining them afterwards. Either search through a cryptic block of code, or keep backups and recompress after every change. While you might save file size, you'll probably lose development time.
Validate your stylesheet online