A userChrome.css file that disables the Firefox tab bar and creates a narrow sidebar on the left side of the screen. When you hover over the sidebar, it expands. If used with the Sidebery extension, it is an elegant and efficient way to display your tabs.
Install the Sidebery extension. Put 'userChrome.css' in your 'Chrome' folder. (More info) Copy and paste the contents of 'sidebery.css' into the 'styles editor' section of the Sidebery settings page. Completely close and reopen Firefox.