Squish
"The Squish for Web edition enables testing HTML-based Web and Web 2.0 (Ajax) applications in different web browsers running on different platforms.
Squish for Web is, unlike many available web testing tools, not restricted to a single web browser or platform. Squish for Web supports running and recording tests for web applications in Microsoft Internet Explorer, Mozilla, Firefox, Apple's Safari and KDE's Konqueror on Windows, Linux, Unix and Mac OS X."