I used to have a group of 3 boxes visible, |a minus|100% |a plus| used to control screen size.

You may have removed the button(s) from the Navigation Toolbar by accident. If you right-click a toolbar item in normal (non-customize) mode then you can remove this item from the toolbar. *"Remove from Toolbar" will remove this item from the Navigation Toolbar and moves it to the Customize palette ("3-bar" Firefox menu button > Customize) *"Move to Menu" will move this item to the "3-bar" Firefox menu button drop-down list *"Move to Toolbar" in the "3-bar" Firefox menu button drop-down list will move this item to the toolbar Open the Customize window and set which toolbar items to display. *"3-bar" Firefox menu button > Customize *if missing items are in the Customize palette then drag them back from the Customize window on the toolbar *if you do not see an item on a toolbar and in the Customize palette then click the <b>Restore Defaults</b> button to restore the default toolbar setup See: *https://support.mozilla.org/kb/customize-firefox-controls-buttons-and-toolbars