Do you mean that the tabs are empty and do not open the web pages?

Firefox can't only restore tabs and windows if there is a sessionstore.js file created. This file isn't present when Firefox is running, but should be created when you close Firefox.

Are the files in the sessionstore-backups folder updated if you check their time stamps?

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.

yes the tabs are empty under the name "New Tab" and do not open the web pages. kindly check the attached images. as for the sessionstore-backups I'm afraid they all have new time stamp which i assume that it overwrite it automatically because i opened it and closed several times trying to restore closed tabs. maybe not...... i dont know. any way what should i do next after finding this file?

Thank you very much again

Try to start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem.

• Switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance
• Do NOT click the Reset button on the Safe Mode start window

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

Use "Firefox > Exit" (Windows: Firefox/File > Exit; Mac: Firefox > Quit Firefox; Linux: Firefox/File > Quit) to close Firefox if you are currently doing that by clicking the close X on the Firefox title bar.

did all the above still no luck ):

I can not be certain, but I don't think the system has been changed further, but in Firefox 33 it was revamped, with more files and a whole new (hidden) folder/directory "sessionstore-backups" with new filenames.

• See also this "sessionstore.js disappears while Firefox 33 is running"
  http://forums.mozillazine.org/viewtopic.php?f=38&t=2881109

I previously posted this

Thought I would post a few links about the improved session restore system introduced in Firefox 33 I haven't tried to manually restore anything since then, and that itself is probably an indication that the new system is more robust and reliable.

• A fairly short straightforward blog, but easy to understand and lists the files involved. http://www.ghacks.net/2014/06/27/mozilla-launches-improved-session-restore-firefox-33/
• More background and detail Firefox, the Browser that has your Back[up]
• For completeness, an public Mozilla document, about the issues involved https://wiki.mozilla.org/Firefox/session_restore

{/questions/1041506#answer-678711}

I previously posted this

Thought I would post a few links about the improved session restore system introduced in Firefox 33 I haven't tried to manually restore anything since then, and that itself is probably an indication that the new system is more robust and reliable.

• A fairly short straightforward blog, but easy to understand and lists the files involved. http://www.ghacks.net/2014/06/27/mozilla-launches-improved-session-restore-firefox-33/
• More background and detail Firefox, the Browser that has your Back[up]
• For completeness, an public Mozilla document, about the issues involved https://wiki.mozilla.org/Firefox/session_restore

{/questions/1041506#answer-678711}

</blockquote>

Thank you vey much that link was very helpful. Problem solved :)