Update: Applicable to Firefox 4 and Firefox 5.
Firefox 4 came with quite an interface change, seeming to grow closer and closer to Chrome. Tabs changed location, buttons moved around, and the status bar disappeared… or did it? Mozilla seems to have received enough inquiries about the missing status bar that they’ve written up a knowledge base article to explain it. If you’re already familiar with how Chrome’s status bar works, then you can understand that Firefox 4’s status bar behaves the same way. If you’d like the status bar to work how it used to, you’ll be happy to know that there is a way to restore it and still keep the rest of the improvements that came with Firefox 4.
From the Firefox 4 What happened to the Status Bar? Firefox Help Page:
Simply put, the status bar shows up when it has something to say. If you hover over a link it will show up to tell you where the link goes and if a page is being loaded, it will show up to display the status of the transfer.
Since many Add-ons tack icons onto the status bar, they’ve been given their own Add-on Bar for those object to reside. You can toggle on or off the Addon bar with the keyboard shortcut Ctrl + /
If you’ve upgraded to Firefox 4 and miss the old status bar, you can download the Status-4-Evar addon to reproduce the classic status bar to your liking. The status bar seems to be one of this divisive things that you have to have like showing extensions in Windows. Because of that, the Status-4-Evar addon has a lot of high reviews from people that were desperate to have it back.