hello sorrelcy, please try to reset firefox and see if this can address the issue...

Thanks Phillip - I'd already reset, to no avail. I tried a right click in the blank area to the left of the tabs, found the activate/deactivate check off and "Bob's your uncle". Got it back to normal.

I'm not sure what you did exactly to fix the problem. Did you right click a blank spot to the RIGHT of the tabs and select Customize? See Customize Firefox controls, buttons and toolbars for how that works. In any case, since you said that you're "back to normal" do you want to mark your last reply as solving the problem?

Your "more system details" show that you have a "Coupons, Inc. Coupon Printer Plugin" installed so it's possible you still have a Coupons, Inc. toolbar extension installed, but just hidden. To remove it and other unwanted add-ons, see Disable or remove Add-ons. I'm not sure what else you may need to do but this page might help: http://www.couponsinc.com/corp/source/u_uninstall.asp

Plugins are usually installed and added by other programs installed on the computer, so you may want to check that in the Control Panel > Programs.

If it happens again:

Make sure that you do not run Firefox in full screen mode (press F11 or Fn + F11 to toggle; Mac: Command+Shift+F).

• https://support.mozilla.org/kb/how-to-use-full-screen

Make sure that toolbars like the "Navigation Toolbar" and the "Bookmarks Toolbar" are visible.

• Firefox menu button > Options
• View > Toolbars (press F10 to display the menu bar)
• Right-click empty toolbar area

Use Toolbar Layout (Customize) to open the Customize window and set which toolbar items to display.

• if missing items are in the toolbar 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 toolbar palette then click the "Restore Default Set" button to restore the default toolbar setup

• https://support.mozilla.org/kb/How+to+customize+the+toolbar (already posted above by Alice)
• https://support.mozilla.org/kb/Back+and+forward+or+other+toolbar+items+are+missing

Problem solved. Thank you, everyone, for your responses.