You can look at the Autohide extension:

Autohide: http://www.krickelkrackel.de/autohide/

thank you. that's just what i wanted.

shame it's not default behaviour though

You're welcome.

Yep, that's what happens when Mozilla includes features that were previously only available with an extension. IMO, they half-ass the job and leave out the "little things" that were in the extension that (IMO) they are attempting to replace.

First it was adding a spellcheck feature to replace SpellBound - and they added the "spellcheck suggestions" to the Context Menu, which is usually already overloaded once the user has installed a few extensions, in lieu of using a floating spelling correction window like SpellBound had. Plus they didn't provide easy access to the Personal Dictionary file, like SpellBound had thru that "floating window".

Second example (although it's not an issue with "enhancement" by replacing an extension) is the "warning / information bar" that appears that the top of the screen when certain actions are done by the user (like installing an addon from a domain that isn't in the "allowed list") or triggered by webpage content (like a missing plugins message) - that bar pushes the page content down like FullScreen does.

Third was the enhancement to the FullScreen capabilities that were in older versions of Firefox. Without Autohide, the user has to watch the browser content bounce down as the cursor is moved to the top of the screen. Plus there's no easily accessible control to always show the Tab strip, as Autohide has had for the last 5 years, or so.

extensions are brilliant way to experiment with new features. They show what users really like and what is the best way to develop a program. It's a kind of perfect democracy really.

Only when developers include new features based on extensions they should do it in a way that most users like.

Unfortunately, the krickelkrackel has been shutdown and I can't install this useful add-on.  :( Anyone have an alternative?

I agree and looked everywhere for http://www.krickelkrackel.de/autohide/ to no avail.

Can someone please change how to make fullscreen not push the page down when toolbars are shown on mouse hover in FF? The toolbars should behave more like IE. This would make FF SO much better. Please dont take the IE comparison the wrong way as FF is quite superior and the ONLY browser I use, but this one thing has got to be changed. It's irritating the way FF pushes the whole web page down while in fullscreen mode when the toolbars are shown on mouse hover.