Firefox Menu > History > Click "Recently Closed Window".

• https://support.mozilla.org/en-US/kb/how-do-i-restore-my-tabs-last-time

That option is grey and not able to be chosen...

Try to restore a previous version of the sessionstore.js file if there is one from a suitable date/time.

• Right-click: Properties > Previous Versions

• http://windows.microsoft.com/en-US/windows7/Previous-versions-of-files-frequently-asked-questions

I could not find a "sessionstore.js" file

What about going into your firefox history and seeing what you visited?

Also, addons like Save my tabs and Session manager could help in these cases.

Also see

• https://support.mozilla.org/en-US/questions/1040776

And please update us on how and if you solve your issue in the meantime.

Yeah. That is what I did but I had to go site by site and did not remember everything I had open so it did not work out well.

In the Bookmarks Manager, create a new folder (Favorite for example) and put the links you want in here.

Sure, if I had done that before I accidentally closed the window it would not have been an issue. Not really a solution, Fred.

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

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

I knew I had seen this somewhere, and finally found it. Open the Firefox menu and click on History. There is a "Restore Closed Windows", followed by a list of the ones most recently closed. Hope this helps.