Enter
about:config in the address bar. Double-click the accessibility.tabfocus line. Enter
3 in the dialog box. (The default is 7.) See
http://kb.mozillazine.org/Firefox_:_...config_Entries for more.
Regards
Simon
EDIT: Oops, this forum software must be buggy, it inserts spaces before colons. There should be no space between "about" and ":config" and the same thing happens in that URL I gave. --Simon