From MozillaZine Knowledge Base
In Firefox’s fullscreen mode, toolbars and the tab strip are hidden at the top of the screen and only shown on mouseover. To draw attention to this, they are shown sliding upwards and off-screen when fullscreen mode is toggled on. This preference determines the behavior of that animation.
Possible values and their effects
Do not animate the collapsing toolbars/tabstrip.
Only animate the first collapse; subsequent collapses are instant. (Default)
Animate every collapse.
First checked in
2008-03-08 by Reed Loden (patch by Michael Ventnor)
Has an effect in