You can check if you have a user.js file in the Firefox profile folder that sets the browser.sessionstore.resume_session_once pref to true.

• http://kb.mozillazine.org/browser.sessionstore.resume_session_once

You can use this button to go to the currently used Firefox profile folder:

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

I went to Firefox profile folder and did not find a user.js file. I now must modify the description of my problem as I have opened Firefox, closed all unwanted tabs, and then during session opened a few to several tabs different from the ones that were opened at start of session and then logged off. I have done this several times, both during times when I have left computer running and after I have shut down computer and rebooted. Every time I start Firefox the tabs that open are NOT from previous session but are always the very same tabs that were opened in the session when I first noticed this problem.

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" - NOT REFRESH!

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.

Thank you so much for your easy to understand suggestion, but as I mentioned in my original post I had just refreshed Firefox to take care of an unrelated problem. The only theme listed in appearance is Default 37.0.2, which I assume is automatically enabled as there is no choice to enable or disable. As for extensions I only have one: Norton toolbar, which was already disabled. I did find hardware acceleration was checked so I did uncheck that to no avail. Any other thoughts or ideas would be much appreciated.

You should see on the Help > Troubleshooting Information page if there is a user.js file detected.

• Help > Troubleshooting Information

user.js Preferences

Your profile folder contains a user.js file, which includes preferences that were not created by Firefox.

Windows hides some file extensions by default. Among them are .html and .ini and .js and .txt, so you may only see the User file name without file extension. You can see the real file type (file extension) in the properties of the file via the right-click context menu in Windows Explorer.

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).

In what section would this elusive user.js file be? Would it sitting right out in the open under one of the section headings like, Application Basics, Extensions, Graphics, Important modified preferences, or any of the others. If so it is nowhere to be found. Now if I have to delve deeper to find it tell me how. Now as to checking problems with sessionstore.js file, I think I'm looking in the right place you have typed Profile Directory: Show Folder as I don't find that exact wording I'm going to Profile Folder: Show folder. In here I have checked every file in every folder and don't find a sessionstore.js file. Must there be one? Generally what would be the name of the folder it would be in? I apologize for being so thick but I just can't seem to find the files you think I should.

First I would check that those unwanted pages didn't get saved into your home page(s) setting: Startup, home page, tabs, and download settings.

If you don't need previous session data, could you try renaming or removing your previous session files? Here's how:

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

• "3-bar" menu button > "?" button > Troubleshooting Information
• (menu bar) 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, either:

• "3-bar" menu button > "power" button
• (menu bar) File > Exit

Pause while Firefox finishes its cleanup, then:

(1) Rename sessionstore.js to something like sessionstore.old. If you see a file named sessionstore.bak, go ahead and delete that.

(2) Rename the sessionstore-backups folder to something like sessionstore-backups-old.

Start Firefox back up again and it should be impossible for Firefox to restore your previous session. But what happens the next time you exit and start Firefox up again? If the long-dead session reappears, then some other software must be modifying your Firefox sessions folder.

You you post the content of the troubleshooting information page?

You can leave out the print. prefs under modified preferences.

• https://support.mozilla.org/kb/Using+the+Troubleshooting+Information+page

My problem has now been solved. I don't know if there is anyone else out there that would end up doing what I did but just on case I will tell you what ultimately was causing the multiple tabs to open each time I opened Firefox, at least as far as I understand it. While I was contemplating the most resent helpful reply in hopes of figuring out what was wrong with my Firefox, my son showed up from out of town, and within 5 minutes he discovered where I screwed up. In Options > General > Home Page, I had an address that included not only the home page I wanted 'Google News', but apparently the addresses to all the other tabs that kept showing up when I started up Firefox. This may not be exactly the correct explanation but changing home page to "news.google.com" solved the problem. Thanks to all out there who gave their best to help me, I'm sure its difficult to solve problems like this when it would never occur to you that someone would do the things they do. Thanks again.