There is very helpful on-line tool that will show you how your web site looks in almost 60 browsers and four platforms (Windows, Linux, Mac OS and BSD).
It will start to create the screenshots of a provided URL in a few minutes, and within an hour it will create all screenshots. You can refresh the page to see the results at any moment.
I tested my website, with default selection of 45 browsers on all platforms and it failed to render properly only in one browser (Safari 1.3.2 on Mac OS X 10.3). So that's a success!
Try your website on http://browsershots.org/. This tool is my recommendation!
