WOW Gold: The quest is given from the same NPC who gave you the quest for positive karma
If you are resurrected by a player, you will not go to jail, but will still have negative karma (unless you had less than -50 WOW Gold, in which case you will become neutral again) and be once again free to kill by players.
Once you are in jail, if your name is yellow or brown, you may wait for your name to become white again over time or you may kill 50 mobs to receive your karma back. If your name is purple, you MUST do a quest to kill 200 monsters, or your karma will NOT go down.
The quest can be obtained from the NPC next to the bank NPC in Kebaras town. After you kill the 200 monsters you were instructed to (Quest mobs are usually 1-3 levels below your current level,) return to the quest giver to have your karma removed.
If you receive a key, (The quest is given from the same NPC who gave you the quest for positive karma) Follow the road north, out of Kebaras town, until you come to a portal, double click your key to use it and congrats!
You are now free from jail, and hopefully this experience has taught you a little something about compassion. (The alternative to the Kebaras quests to remove your karma is a Scroll of Forgive, which can be bought in the Cash Shop.)