Firefox 4 is supposed to save your session (and history) automatically. It no longer offers to save the tabs when you shut down. If you are clearing your history automatically this cannot happen, so I would check the settings in Options > Privacy > and the Settings button next to "Clear history when Firefox closes". If it is set to clear history, you need to uncheck that.

One of the changes in Firefox 4: '''''by default''''' Firefox 4 does not display the "Save Tabs and Exit" warning message when closing multiple tabs, but it can be turned back on by changing some preferences. *<u>Saving tabs was not removed from Firefox 4</u>, but it works a bit differently. *By default, Firefox 4 will not ask to save tabs, but instead it will always '''''automatically''''' save your tabs on exit <u>unless you are in Private Browsing mode</u>. You can restore them next time by: *#clicking Firefox button > History >"Restore Previous Session", or *#type '''''about:home''''' in the URL bar and press the Enter key, then press the "Restore Previous Session" button *#See: https://support.mozilla.com/en-US/kb/Firefox%20does%20not%20ask%20to%20save%20tabs%20and%20windows%20on%20exit *''<u>Note: This was a decision by the developers. On this forum, we are all '''uncompensated volunteers''' here to help other users. The developes/employees of Mozilla/Firefox rarely, if ever visit here.</u>'' To display the "Save Tabs and Exit" message when closing multiple tabs, you can do the following: #Type '''''about:config''''' in the URL/Location/Address bar and press the Enter key #Accept the warning message (promise to be careful) #The preferences page/list will open #Filter = '''''browser.tabs.warnOnClose''''' #If its value is set to false, double-click on it (in the lower panel) to toggle its value to true #Repeat steps 4 and 5 for these following 3 preferences also: #*'''''browser.warnOnQuit''''' #*'''''browser.warnOnRestart''''' #*'''''browser.showQuitWarning''''' #**Note: last pref is new in Firefox 4b12, may need to add (boolean) #**Info/Instruction for using '''''about:config''''': http://kb.mozillazine.org/About:config #See: #*https://support.mozilla.com/en-US/questions/785169 #*http://forums.mozillazine.org/viewtopic.php?f=23&t=2105039&p=10434467&sid=fd2a35945bb2c633687f7b50d8c53989 #*http://blog.zpao.com/post/3174360617/about-that-quit-dialog Some things to check if your tabs are not being saved when closing Firefox 4: #'''Browsing history must be saved''' #*Firefox button: Firefox button > Options > Options > Privacy > [X] Remember my browsing history #*Menu Bar: Tools > Options > Privacy > [X] Remember my browsing history #'''Also make sure you do not clear "Browsing History" when using Clear Recent History or when closing Firefox''' #*Using Clear Recent History #**Firefox button: Firefox button > History >Clear Recent History #**Menu Bar: Tools > Clear Recent History #*When closing Firefox #**Firefox button: Firefox button > Options > Options > Privacy (checked) > Settings #**Menu Bar: Tools > Options > Privacy (checked) > Settings #**See: https://support.mozilla.com/en-US/kb/Clear%20Recent%20History #'''Make sure you are not in Private Browsing mode''' or '''in permanent Private Browsing mode''': #*See: https://support.mozilla.com/en-US/kb/Private%20Browsing #'''If you have the'''Tab Mix Plus''' extension''', then disable the built-in session restore.