Usage: ISON nick [nick ...]

Queries the server as to the current status of the given nicknames.
If the nicknames are currently on irc, their nicknames will be returned
in a 303 numeric message.  If they are not on irc currently, their
nicknames will not be returned.

Hooking the 303 numeric is a bad idea becuase it messes up the NOTIFY 
feature of ircII because the ISON command is how the NOTIFY command
works.

See Also: NOTIFY

