Before trying to use the time machine (which I do not understand anyway) please look for all profiles on your Mac including any on the Desktop in a folder called old firefox data Please then back up those profiles somewhere safe & not in a Firefox program or profile path. (or at least backup any folder sessionstore-backups )

Recent versions of Firefox automatically try to backup your session state on separate occasions and so there should be no need to use the timemachine.

if something went badly wrong and the profile is corupt or could not be found Firefox may have created a new profile. Please search for the file places.sqlite . Such files probably only exist in Firefox profiles, and should be present in every profile.

Please post back to say what you find.

Hi, many thanks for your reply. I have searched for both the "old firefox data" and the "places.sqlite" but I cant seem to find them. I am not sure of they might be hidden. I have done this once before by finding an older version of the correct file on the Time machine. But it seems as though I cant actually find the current correct file either.....

Sorry I use Linux & Windows but not Mac s If you can find ALL the files places.sqlite we should then be able to find the profile locations and then the files you need to get back the 300 lost tabs.

Possibly you do need to make sure you can see hidden or system files and also that you can see the file extension that is the part after the dot. For instance dot places or dot txt. On Windows that part not only indicates the type of file it is vital in determining the correct actions. You also need to make sure you are searching the corerct pahs and preferably you are searching the whole of the hard disk space including sub folders.

If you open your Firefox profile folder from the troubleshooting page you should be able to see places.sqlite within the Finder just by looking at the listing. Once you have satisfied yourself that the file is their can you try searching again.

Note that the Firefox profile is normally a hidden location in Linux and presumably in a Mac it will have folder names that start with a dot.

• Windows users look at this mozillazine help article
  Finding the profile folder on Windows
  http://kb.mozillazine.org/Finding_the_profile_folder_on_Windows#Viewing_hidden_files_and_folders
• Mac http://kb.mozillazine.org/Show_hidden_files_and_folders#Mac_OS_X

Whilst those tips will help you find the current places file I am not entirely sure how to set Finder or Spotlight to show all hidden files possibly these articles help

• MacTips&Tricks: Show Hidden Files On Your Mac – Works In Mountain Lion 10.8
  http://www.mactricksandtips.com/2008/04/show-hidden-files.html
• Lifehacker How to Search for Hidden, Packaged, and System Files in OS X
  http://lifehacker.com/5711409/how-to-search-for-hidden-packaged-and-system-files-in-os-x

OK, I have managed to locate the folder! What shall I do next? I think Time Machine is relatively straight forward, so if necessary, it might be possible to 'go back in time' via the time machine and locate the places.sqlite file before I lost the information and use this file to replace the one my system is currently using...just a thought

Hi, thanks for all of the help so far, but i am still a bit stuck because I am not too sure what to do after finding the file. Thanks again