Ultimate JavaScript Client Sniffer creates is_ variables:
booleans: is_nav2, is_nav3, is_nav4, is_nav4up, is_nav5, is_nav5up,
is_ie3, is_ie4, is_ie4up, is_ie5, is_ie5up, is_opera
integer: is_major (version number)
float: is_minor (version number)
booleans: is_win95, is_winnt, is_mac68k, is_unix ...