A couple of days ago I was buried in the wonderful world of browser compatibility. A redesign of this site was working in Firefox but not in IE6. The struggle, of course, is testing my code in various flavours of different browsers on different platforms. This is where Browsershots is a life saver.
Browsershots makes screenshots of your web design in different browsers. It is a free open-source online service created by Johann C. Rocholl. 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 make screenshots and upload them to their central server.
On Linux, I saw this site behaving properly in Epiphany 2.20, Firefox 1.5, Firefox 2.0, Konqueror 3.5 and Opera 9.24. In Windows, I saw this site behaving properly in Firefox 1.5, Firefox 2.0, MSIE 6.0, MSIE 7.0, Opera 9.24 and Safari 3.0. In the Mac OS I saw everything looking great in Firefox 2.0 and Safari 2.0. I also saw that there are issues in Windows in MSIE 5 and MSIE 5.5. If you're still using a version of Internet Explorer that pre-dates 6, you'll see the left sidebar overlaps the main content. You're also out of luck because I've decided not to care about you. Upgrade your browser!
I highly recommend Browsershots for web authors. It's a fantastic service and you can't beat the price.