HELP ME TO CAPTURE FUNCTIONAL KEYS LIKE F1 F2 IN NETSCAPE BROSER

HI I AM TRYING TO WRITA A JAVA SCRIPT.
MY REQUIRNMENT IS 
1)IF I PRESS F2 IT MUST POP UP A HELP BOX 
CAN ANYONE PLEASE WRITE ME A PIECE OF CODE THAT CAN DO IN NETSCAPE ELAVBELED
BROWSWER
EITHER IN HTML.JAVA SCRIPT
THANKS
MAHESH