Make sure that, its unchecked the "Always use private browsing mode" *https://support.mozilla.org/en-US/kb/settings-privacy-browsing-history-do-not-track#os=winxp&browser=fx17

Note that the "Use custom settings for history" selection allows to see the current history and cookie settings, but selecting this doesn't make any changes to history and cookie settings.<br /> Firefox shows the "Use custom settings for history" selection as an indication that at least one of the history and cookie settings is not the default to make you aware that changes were made.<br /> If all History settings are default then the custom settings are hidden and you see "Firefox will: (Never) Remember History" (Never remember history means that Private Browsing mode is active). "Use custom settings for history" stays selected if at least one of the History or Cookie settings is not the default to make you aware that changes from the defaults are made. Start Firefox in <u>[[Safe Mode|Safe Mode]]</u> to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance). *Do not click the Reset button on the Safe mode start window or otherwise make changes. *https://support.mozilla.org/kb/Safe+Mode *https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes If you do not keep changes after a restart then see: *http://kb.mozillazine.org/Preferences_not_saved