This is a Firefox addon to help take the pain out the Finder box in the bottom left. One of the most annoying things to me is typing --in particular inside of a new message or a reply in gmail--and then for some reason I always get caught in the finder box and can't lose the focus unless I click that circled x.
It has nearly caused me to throw my laptop through the window on several occassions. What this addon does is it lets you click Control+F to close it -- the same way you click Command+F to open it. So, in the event that you get trapper in there, you can just click Control+F to get out and continue doing whatever you were doing.
To install it, click here: