Hi, try this: Type about:config into the address bar, press Enter, accept the warning and scroll down to extensions. and you may be able to find a clue to its name, since Add-ons that are removed often leave their settings behind.

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Im looking at that but it makes no sense to me at all. I really dont know what i am looking for, its all nonsense :-/

You would have to inspect a copy of the extensions.ini file to see the names of all extensions that you had installed.

If you use(d) the Time Machine then try to inspect or restore the file(s) from that backup.

• http://www.apple.com/support/timemachine/

• http://kb.mozillazine.org/Profile_folder_-_Firefox
• https://support.mozilla.org/kb/Recovering+important+data+from+an+old+profile
• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox