Here's a little gotcha in Firefox 3.0 for web site designers. My website was incorrectly formatted in Firefox 3, but worked fine in Firefox 2. I had some JavaScript code that did the following:
mainTabDiv.style.left = (mainTabBarLeft-mainTabBarDX)+'px;';
mainTabDiv.style.top = mainTabBarTop+'px';
With that code in Firefox 3, mainTabDiv was not positioned correctly -- it was at 0. So I put in an alert:
left= mtbl=270 mainTabBarDX=2
Can you spot the problem? The first statement in my source has px; and the second one has px. That is, the failing statement had a semicolon at the end of the string. In Firefox 2 this worked OK. In Firefox 3, the assignment does nothing. So check your JavaScript for stray semicolons if you're having site issues in Firefox 3.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20080708162942195