Browser.sessionstore.max resumed crashes
From MozillaZine Knowledge Base
The Session Restore feature allows the user to continue browsing from where they left off if the browser restarts. This preference was added in Firefox 3.5 and above to control the number of crashes that can occur before the "about:sessionrestore" page is displayed. By default, the previous session is automatically restored once. The user is asked which pages to restore after the second crash.
Possible values and their effects
The number of crashes that can occur before the "about:sessionrestore" page is displayed. Default is 1 (the last session is automatically restored once). Note: This preference has no effect if more than 6 hours have passed since the last crash. 
Set the preference value to 0 if you do not want the previous session automatically restored after a crash or unexpected close. 
First checked in
Has an effect in