Pressing F11 in Firefox displays the current website in full screen mode removing many of the toolbars and buttons that are not required to view a website. There is however no obvious possibility to change the appearance of the full screen view mode of Firefox.
Autohide is a Firefox extension that lets you configure the full screen display mode the way you want it to be. If you do need the status bar for instance you can add it to the full screen display mode so that it is always visible while in that mode. All installed toolbars can be hidden or displayed depending on the choices that you make in the settings of Autohide.
Other options let you see or hide the Windows taskbar when in full screen mode or disable context menu entries. Autohide is a small extension with great impact on the way the full screen mode is displayed. Very useful if you tend to use this mode regularly.

Update: Autohide is now available under a new website address.
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Once again, I found the solution to a problem in ghacks.
I love this site! :D
This add-on has virus, be careful. This is the reason that the author do not publish it on official mozilla add on’s website.
Are you sure, Lucas? What virus? I didn’t had any problems with it…
You have to be suspicious of any updates not on Mozilla’s official website.