As is IE9, this restartless add-on combines the navigation and tab toolbars into one line to give more space to web pages. To combine the navigation and tabs toolbars, the location bar is given a small fixed size while the search bar is collapsed to a single button.

How to Install and Use Oneliner Firefox add-on

  1. Download and install OneLiner add-on. It is a restartless add-on, so your Firefox does not need restart. After installing it, the add-on combines navigation bar and tab bar into one-line.
  2. To perform searches with Search button, enter keywords and click search button or simply press enter button.
  3. You can use Ctrl+ K shortcut instead to activate in-tab search bar. Note: Location bar expands to cover back or forward buttons when they are not in use. One-line will visible even in full screen mode, because it does not get auto-hidden. (via) You can install Oneliner Firefox add-on from Mozilla add-on site.