I continually get greeted with the “restore last session” pop-up when I start firefox. I find it really annoying especially as I use Google Browser sync to do exactly the same thing, so I have to deal with two restore messages. I have followed the following link and turned off the session restore feature in firefox.
1. type about:config in your browser URL
2. go to the browser.sessionstore.enabled setting
3. change the setting to false