Enable Firefox "Save & Quit"

I liked the option of "save & quit" in the mozilla firefox, but unfortunately I can't find it in the new version. I discovered that you can get it back :) .. I followed these steps from [1] and it worked.

First

1. Type about:config into the location bar and press enter
2. Accept the warning message that appears, 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 these 3 preferences browser.warnOnQuit, browser.warnOnRestart and browser.showQuitWarning"

Second 

You need to set: Firefox/Tools > Options > General > Startup: "When Firefox Starts": "Show my home page". and your favourite firefox pop up "Save and Quit" question will appear again. If the last option is set on "Show my windows and tabs from last time" the browser won't ask you anything when you're closing it. ENJOY :)

Reference:
[1] http://support.mozilla.org/en-US/questions/753984#answer-104921