boovyeh said

Each time I open Firefox it immediately opens 86 to over 200 tabs. I can't find any way to return Firefox opening to normal. I am running Yosemite 10.10.2 on my Mac.

Hello,

Try Firefox Safe Mode to see if the problem goes away. Firefox Safe Mode is a troubleshooting mode that temporarily turns off hardware acceleration, resets some settings, and disables add-ons (extensions and themes).

If Firefox is open, you can restart in Firefox Safe Mode from the Help menu:

• Click the menu button , click Help and select Restart with Add-ons Disabled.

If Firefox is not running, you can start Firefox in Safe Mode as follows:

• On Windows: Hold the Shift key when you open the Firefox desktop or Start menu shortcut.
• On Mac: Hold the option key while starting Firefox.
• On Linux: Quit Firefox, go to your Terminal and run firefox -safe-mode
  (you may need to specify the Firefox installation path e.g. /usr/lib/firefox)

When the Firefox Safe Mode window appears, select "Start in Safe Mode".

If the issue is not present in Firefox Safe Mode, your problem is probably caused by an extension, theme, or hardware acceleration. Please follow the steps in the Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems article to find the cause.

To exit Firefox Safe Mode, just close Firefox and wait a few seconds before opening Firefox for normal use again.

When you figure out what's causing your issues, please let us know. It might help others with the same problem.

If the problem didn't disappear in Safe Mode, reset your Firefox startup settings. They could be set to open those tabs:

1. Click the Menu button (located in the top right corner of the window).
2. Click "Options".
3. Click the General tab.
4. Click the "Restore to Default" button.
5. Choose "Show my home page" next to When Firefox starts.
6. Click the "OK" button.

What are the websites that are opening?

You can check for problems with the sessionstore.js file in the Firefox profile folder that store session data.

• Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder)
• http://kb.mozillazine.org/Profile_folder_-_Firefox
• http://kb.mozillazine.org/Multiple_profile_files_created

Deleting sessionstore.js will cause App Tabs and Tab Groups and open and closed (undo) tabs to get lost and you will have to recreate them (make a note or bookmark them if possible).

If Firefox is your default browser, clicking a link in another application should launch that link in Firefox without opening either your home page or your previous session.

If you don't have a link handy, it might also work in a system search box to type or paste http://mozilla.org and press Return.

Once Firefox starts, you should be able to investigate the above actions without fighting all the tabs.

Thanks, Just-A-User, but I don't get any web sites, just tabs with empty pages below.

You can check for problems with the sessionstore.js file like I posted above.

Thanks Cor-el and jscher. The Firefox Safe solution above worked. All is well.