First check a setting for how Firefox opens. # Open the options dialog - in the Tools menu select Options # In the Options dialog select the General panel # Make sure the setting "When Firefox starts" is set to "Show my windows and tabs from last time" If it is already set to that, there may be a problem with the file that stores details of sessions. # Open the profile folder, for details of how to access it see [[profiles]] # Close Firefox # In the profile folder delete sessionstore.js, plus if it exists sessionstore.bak Hopefully, when you next close and re-open Firefox it should rmember the sessions.