Browser compatibility is just one of the many factors that must be taken into consideration when building a web site. Not everyone has the same screen size or resolution, and the different browsers available for people to view the web vary considerably when it comes to displaying web content. Here are a few tools I have found to help with browser compatibility issues.

The Web Developer Extension for Firefox, Flock, and SeaMonkey by Chris Pederick is a MUST-HAVE for all web developers!
Download Web Developer Extension for Firefox Here