There were some changes in Firefox 4 default settings for some of the warning messages. You can set this hidden pref to what you want, to give the warning when closing multiple Tabs.

1. Type about:config into the location bar and press enter
2. If you see the warning about accessing those prefs, you can confirm that you want to access that page.
3. Type browser.tabs.warnOnClose in the Filter line at the top, and that pref will appear. If its value is set to false, double-click on it to change its value to true.
4. Then restart Firefox.

You can repeat that for these 3 preferences - browser.warnOnQuit, browser.warnOnRestart and browser.showQuitWarning, if you want to change those too.

I had this problem too, thanks very much the-edmeister. The preference to be set in order to bring back the save and quit function the OP mentioned is browser.showQuitWarning to true.

I'm not loving FF4 at all. It forced me to ugrade then promptly couldn't add my addons. Had to hunt round for a way of getting photobucket to work on it. Had to alter the config manager. The save and quit feature doesn't exist anymore, which was why I preferred FF in the first place. The font looks all scewed and weird ~ if it doesn't improve I'm moving on to a browser that does support everything I want on it. Come on FF I've been a loyal user for a long time and this is annoying me.

I tried this solution and it worked at first but now it isn't and all the settings are still the ones listed above. Any ideas?

Firefox 4 saves the previous session automatically, so there is no longer need for the dialog asking if you want to save the current session.
You can use "Firefox > History > Restore Previous Session" to get the previous session.
There is also a "Restore Previous Session" button on the default about:home Home page.

Another possibility is to use:

• Tools > Options > General > Startup: "When Firefox Starts": "Show my windows and tabs from last time"

Do not use Delete browsing, search and download history on Firefox to clear the 'Browsing History' when you close Firefox.

Thanks the-edmeister for this excellent solution....