Try to reset Firefox:

https://support.mozilla.org/kb/Basic+Troubleshooting

and also visit this link, Hope it helps

http://support.mozilla.com/en-US/kb/Session%20Restore#w_configuring-session-restore

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

• http://kb.mozillazine.org/Preferences_not_saved

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

• Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder)

It say it set to true ... I have not updated yet but that because of my security software doesn't have patch for there toolbar yet so I hope it will fix itself then - will it?

You can delete the user.js file if that what your above reply is about to prevent Firefox from restoring the previous session on each start.

Is safe to do so? I couldn't find under profile folder - I add to search for it but is okay to deleted? If so what the safest way of doing it - just deleting the file like that?

Note that Windows hides some file extensions by default.
Among them are .html and .ini and .js and .txt, so you may only see the 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.

Can you post the content of the user.js file?

> Firefox > Profiles > ec6p37cr.default

So it's in the ec6p37cr.default which I search for in there and the tittle of it is User .... I haven't click on while I'm not using firefox yet so ... I'll see

I still get an error if I click on it would a pic help? If so I do it tomorrow when I get back

Thank you for helping me so far.

You shouldn't double-click a Firefox .js file as that will make Windows try to run this file as a JScript file and this will fail because it is a Firefox file that stores user set prefs.
To inspect the file, you need to access the right-click context menu and use "Open with" to open the file in a text editor like Notepad.

I open it with notepad -

user_pref("browser.sessionstore.resume_session_once", true);

Yes, that line will cause Firefox to restore the previous session at each new start, so you need to delete this file to prevent this.

okay I test it out

It seems to work so why is that the case?

When the browser.sessionstore.resume_session_once pref is set to true then it does what it says and restore the previous session.
You may have had an extension or other software on your computer that had created this file (the file creation date might give a clue).