Firefox: hide tab-bar completely

When using a vertical tab extension like Vertical Tabs Reloaded, you can hide the tab bar by adding the following line to userChrome.css:

TabsToolbar { visibility: collapse !important; }

See multi row tabs for instructions on how to find the userChrome.css file.

This mode may require changing the way new tabs open. Set browser.tabs.insertAfterCurrent and browser.tabs.insertRelatedAfterCurrent (in about:config) according to this table:

open all tabs next to the current tabtruewhatever
open all tabs at the end of the tab barfalsefalse
related tabs next to current, others at the endfalsetrue