I recently installed OS X Leopard on my machine and one feature that I particularly liked was the Spaces utility. It allows for multiple virtual desktops that you can switch between.
However, when I've been switching between spaces using Command+Tab from lets say Textmate to Firefox, to see my websites development, Firefox has lost focus. So would have to manually click on the window with my mouse each time I wanted to refresh the page. Very utterly annoying. Until today, when I installed Firefox 3 Beta 1 which not only comes with a nice smoother look, but also with this focus bug wiped out. yay!
Too bad Beta 1 doesn't support my Firebug plug-in, doh!
Update: Firebug for Firefox 3 Beta 1.