LeechBlock is a simple productivity tool designed to block those time-wasting sites that can suck the life out of your working day. All you need to do is specify which sites to block and when to block them.
GNOME 3 theme for Firefox — Previously known as "Adwaita"
Hide title bar if window is maximized.
This extension created only for GNOME 3. It can create problems with another DE (KDE, XFCE, etc). However, you can use HTitle at your own risk (need enable "legacy" mode on settings page).
Provides better integration with Gnome using standard notifications and other features