Not saving History (Tools -> options -> Privacy), make sure you are saving your history in the privacy options, and also not clearing in "Settings for Clearing History", see

• http://img232.imageshack.us/img232/4928/clearcachew.png

You can uncheck the "Clear history when Firefox closes" but you still have the the "Clear recent history" (formerly "Clear history") loose canon on the Tools menu, best to make sure that the only thing you clear when you exit Firefox is the browser cache.

A way to do that is to lock the corresponding privacy.cpd and privacy.clearOnShutdown pref(s) on the about:config page via a mozilla.cfg file in the Firefox program folder (C:\Program Files\Mozilla Firefox\).

• http://kb.mozillazine.org/Locking_preferences

Be aware that it is still possible to clear the history in the sidebar and the History/Bookmarks Manager (History > Show All History)

//first comment line in mozilla.cfg required
lockPref("privacy.clearOnShutdown.history", false);
lockPref("privacy.cpd.history", false);

You can place a file local-settings.js in the defaults\pref folder with this content:

pref("general.config.filename", "mozilla.cfg");
pref("general.config.obscure_value", 0);

If you set the obscure value to 0 then no byte-shift is required.