What is H4xx?
1.
if playing a computer game, and you experience loosing big, and feel that it is unacceptable, and you wish to blame your opponent for cheating but don't want to ruin your reputation (calling people for cheaters is lame, since mostly you just suck and the other player is pwning you) you can write h4xx to indicate that it is an uneven battle or fight, but your opponent will simply smile or write "k noob" which is considered to be a friendly reply
Loser: h4xx, this i lame
winner: lol k noob.
See