Flexible spacers do not work on a toolbar that has items with a flex property like the location bar and the Google search bar. You can adjust the padding and the margin with code in [http://kb.mozillazine.org/UserChrome.css userChrome.css] See http://kb.mozillazine.org/Editing_configuration#How_to_edit_configuration_files You can also look for a compact theme on the add-ons site. *https://addons.mozilla.org/en-US/firefox/themes/compact *https://addons.mozilla.org/en-US/firefox/addon/3699/