See: * http://kb.mozillazine.org/accessibility.tabfocus Note: In OS X (as of 2005-01), if this preference is not explicitly set, the “Full Keyboard Access” setting in System Preferences will be honored. All builds before that date (e.g., Firefox 1.0.x) will ignore that setting. This pref doesn't exist by default, so if you want to use it instead of the system settings then you need to create a new Integer pref with the name accessibility.tabfocus and set the value to what you want (7 is to tab through all the fields).