For some reason, your preferences have been changed to not save any closed windows or tabs. To restore those, you'll need to visit the about:config preferences editor.

(1) In a new tab, type or paste about:config in the address bar and press Enter. Click the button promising to be careful.

(2) In the search box above the list, type or paste sessions and pause while the list is filtered

(3) Either right-click > Reset or double-click to edit these preferences:

(A) For tabs: browser.sessionstore.max_tabs_undo (default=10)

(B) For windows: browser.sessionstore.max_windows_undo (default=3)

This won't help with tabs closed in the past, but should work going forward.

A few other notes based on what's listed in your More System Details:

(1) A user.js file can override both Firefox's default settings and your own changes. You can find the file and review/delete it using the steps in this article: How to fix preferences that won't save.

(2) The "Surfing Protection" feature of Advanced SystemCare may undo your settings changes. You might want to turn off that feature.

(3) The avast! Online Security extension has been associated with some random bugs. If you notice that some pages are not loading completely, try disabling this extension.

so i just need to follow those instructions and i can have my tabs back also is it possible to change max windows to four or would that make things unstable or something

I think you should go ahead and try 4 if you like. For what it's worth, I've set mine to 20 tabs and 10 windows. This certainly will increase the the size of the sessionstore.js file that stores the information on open and closed windows and tabs, and incrementally increase the time required to update it. If you find that performance is dragging, you could reduce the amount you store, or reduce the frequency of updates (every 15 seconds by default), or see whether something else might be interfering.

ok thanks so much for the help is there any way to prevent my setttings from being changed like that in the future

Well, in theory, features like Surfing Protection in ASC will lock your settings and restore them if they are changed, so you could explore whether that actually works.

With business users in mind, Firefox has a feature to lock some settings so they cannot be overridden. This involves creating a couple of different files in Firefox's program folder (the one under C:\Program Files (x86)\). I haven't tried it myself, but you can read more about it here:

• Locking preferences - MozillaZine Knowledge Base
• Customizing Firefox - Autoconfig Files | Mike's Musings

ok thanks again

there is a much easier way to retain all your open tabs when closing firefox,,dont close it crash it hit ctr-alt-del at same time,,,this brings up the task manager goto the processes tab, click on firefox.exe then right click this bring up a small menu, then click end process or end process tree. this will crash firefox. but when you restart firefox knows it crashed and goes to the session restore page and you will even have the option of which tabs to reopen

Hi smurfxyz, that should work as long as Firefox wasn't updating files at the moment you crash it, which could corrupt them. Personally, I would consider "End Process" a last resort.