Firefox: Restoring the save and quit on Firefox

Firefox v4+

To restore save my session upon exit for Firefox browser after v3:

Steps:

1. Open a new tab, type “about:config” in the address bar

2. Accept "you promise to be careful" message,

3. search for an option: "browser.showQuitWarning" and set it to true

firefox-aboutconfig1

Note: you can also you also can look at these warn prefs on the 'about:config' page and toggle the value to true via the right-click context menu or double click with the left mouse button.

browser.warnOnQuit
browser.warnOnRestart 
browser.tabs.warnOnClose
browser.tabs.warnOnCloseOtherTabs

Note2: on newer firefox version:

Goto: Tools > Options > General > Startup > check 'Restore previous session'.

firefox-aboutconfig2

For more detailed steps, you can use:

Steps:

1. Type about:config into the location bar (address bar) and press enter

2. Accept the warning message "you promise to be careful", you will be taken to a list of preferences

3. Locate the preference: browser.tabs.warnOnClose, if its value is set to false, double-click on it to change its value to true

4. Repeat this for: browser.warnOnQuit and browser.showQuitWarning"

5. Set from menu Tools > Options > General > Startup > When Firefox Starts: > Show my home page.

Note: If you set step 5 to "Show my windows and tabs from last time" the browser won't display the Save and Quit dialog.