If your starting out in web-design or CSS styling then here are some useful websites I came across and use as reference to practice or work something out:
Install Web Developer on your Firefox browser, really useful web tool to help you work out what CSS is doing to a page layout.
CSS Zen garden is a great site to view lots of CSS layouts and work out how they were made whilst also providing inspiration
A great site for test out code or finding the right code for the job, the site also provides practice pages where you can see what the code is doing.
W3Schools - http://www.w3schools.com/