Originally a typo that became popular due to it's humorous appearance in chat windows. The intended word was "w00t" w00t is elite speak (or "l33t") meaning "hurray! or "congratulations!" etc. In some organizations w0t0 is used as a greeting.
System Foud has logged into the channel.
Foud: w0t0!
Kronice: w0t0 bro!
Mindgames: w0t0