Save Tabs when Quitting Firefox 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18...

When quitting Firefox, back in the day it offered to save your tabs:

Do you want Firefox to save your tabs for the next time it starts?

Firefox no longer offers to "Save and Quit" by default, but it's an easy fix to get Firefox to ask this question again.

Open a new tab and, rather than visiting a website, go to "about:config" (without the quotes).  In the filter bar that shows up, type in "showQuitWarning" (again, no quotes).  Double-click to change the value to "True" and, because this is a modified setting, it should turn bold.  Now, when quitting Firefox (only the last open window tho, not every Firefox window, so the Downloads window might mess this up for you if it is open!), you should be offered to save your tabs for the next session.  If you checkmark the "Do not ask next time" box, it will reset your "showQuitWarning" setting.

Click to embiggen

UPDATE: If this change alone doesn't work you may need to also toggle (with a double-click) these settings in that about:config page:

• browser.tabs.warnOnClose 
• browser.warnOnQuit 
• browser.warnOnRestart

This works great on my Firefox 4, 5, 6, 7, 8, 9, 10, and even prerelease versions for Firefox 11, 12, and 13.  This should also work on Debian's Iceweasel and other Firefox clones.  If anyone has tips about improving this let us know!