Every web developer should know this site

What is Browsershots?
Browsershots makes screenshots of your web design in different operating systems and browsers. It is a free open-source online web application providing developers a convenient way to test their website's browser compatibility in one place. When you submit your web address, it will be added to the job queue. A number of distributed computers will open your website in their browser. Then they will make screenshots and upload them to our central dedicated servers for your review.
Source http://browsershots.org/