Here’s a nifty feature I recently discovered on FireFox 2: Recently Closed Tabs. It’s good that it has been standard for FireFox to warn you if you’re closing multiple tabs. After all, Control-Q (or CMD-Q for the Mac) is dangerously close to Control-W (or CMD-W). I’ve fallen victim to this mistake many a time with Safari, as it gives no warning when closing windows with multiple tabs. But neither browser warns you when you close a single tab. I’ve fallen victim to mistaken middle-clicking on FireFox myself many times, which closes a tab.
You can access the recently closed tabs list under the History menu. It gives you the option to re-open tabs you’ve closed while in a particular session. You can also open all recently closed tabs in a new tabbed window. When you close the browser, the list is cleared.
It won’t help if you have unsaved forms filled up when you close a tab, as the Recently Closed Tabs feature won’t bring these back (but FireFox 2’s session recovery feature will, though this only works if FF2 crashes and not when you close it normally). Still, this is a useful feature–a good way to revisit closed tabs, instead of having to dig through your browser history.