The Reset Firefox feature can fix many issues by restoring Firefox to its factory default state while saving your essential information. Note: This will cause you to lose any Extensions, Open websites, and some Preferences.

To Reset Firefox do the following:

1. Go to Firefox > Help > Troubleshooting Information.
2. Click the "Reset Firefox" button.
3. Firefox will close and reset. After Firefox is done, it will show a window with the information that is imported. Click Finish.
4. Firefox will open with all factory defaults applied.

Further information can be found in the Refresh Firefox - reset add-ons and settings article.

Did this fix your problems? Please report back to us!

It doesnt solve the problem. BTW I didnt install firefox using any package manager, but extracted and executing the executable file.

Try to toggle the browser.tabs.onTop pref to false on the about:config page.

• http://kb.mozillazine.org/about:config

A Firefox restart is necessary to update the menu entry to either show or remove it.

It changed the position of the tab but issue is not solved yet :(

You can check for problems with the localstore.rdf file and try to delete the file.

• http://kb.mozillazine.org/Corrupt_localstore.rdf

Removing localstore.rdf didnt help either.

I have downloaded 64 bit firefox http://releases.mozilla.org/pub/mozilla.org/firefox/releases/latest/ following this link. (By default mozilla download site gave i686 version)

Installing 64 bit firefox solved the problem.

Thank you very much for your help cor-el and jayakumar