YHBT// [Usenet: very common] Abbreviation: You Have Been Trolled (see troll, sense 1). Especially used in "YHBT. YHL. HAND.", which is widely understood to expand to "You Have Been Trolled. You Have Lost. Have A Nice Day". You are quite likely to see this if you respond incautiously to a flame-provoking post that was obviously floated as sucker bait.
you have been trolled