Did you install any extensions that affect the Add-on bar?

To rule out extensions as an issue, you could test in Firefox's Safe Mode. That's a standard diagnostic tool to deactivate extensions and some advanced features of Firefox. More info: Diagnose Firefox issues using Troubleshoot Mode.

If Firefox is not running: Hold down the Shift key when starting Firefox.

If Firefox is running: You can restart Firefox in Safe Mode using either:

• "3-bar" menu button > "?" button > Restart with Add-ons Disabled
• Help menu > Restart with Add-ons Disabled

and OK the restart.

Both scenarios: A small dialog should appear. Click "Start in Safe Mode" (not Refresh).

Any improvement?

Also, it goes without saying that Firefox 21 is dangerous to use on the web due to its numerous unpatched, publicly disclosed security flaws.

If you can't stand how Firefox 29+ looks and can't find a fix for it, perhaps you should consider using SeaMonkey (or another browser based on core Firefox code) with an old-timey interface that is being kept up-to-date.

Firefox 21 doesn't have the 3-bar, but I found the safe mode restart. The bar is gone in safe mode. I downloaded classic theme restorer, while on firefox 39, but it doesn't show up in my current addon list. It isn't supported in 21.

Hmm, it sure looks like the Add-on bar, but it's not? Is there any "extra" Add-on bar on the toolbar list? Either:

• right-click a blank spot on the tab bar (or the "+" button)
• View > Toolbars

If the problem can't be tracked down to a particular extension, perhaps the toolbar customization file got corrupted somehow. You could try this, it will reset your toolbars back to defaults:

Open your current Firefox settings (AKA Firefox profile) folder using either

• Help > Troubleshooting Information
• type or paste about:support in the address bar and press Enter

In the first table on the page, click the "Show Folder" button. This should launch a new window listing various files and folders in Windows Explorer.

Leaving that window open, switch back to Firefox and Exit using File > Exit

Pause while Firefox finishes its cleanup, then rename localstore.rdf to localstore.old.

Start Firefox back up again. Is that bar gone?

I added the addon bar to show that it's a different bar. Also the classic theme restore shows up despite being incompatible with firefox 21. Maybe I need to redownload 39 to uninstall it.

http://i.imgur.com/U9eaxiJ.png

I redownloaded firefox 39 to uninstall classic theme restorer and now the bar is gone. Thanks for the help and quick replies.