1.5pre, SMP : Placing a map into an item frame adds a green arrow to the map, at the player's location, pointing in the opposite direction of the player. Doing this again adds another similar arrow to the map, up to a maximum of four. These arrows persist until the server is stopped and restarted: this removes all green markers from all maps, except those are in item frames, which retain one marker at their current location.
David A. Brown
1.5pre, SMP : Placing a map into an item frame adds a green arrow to the map, at the player's location, pointing in the opposite direction of the player. Doing this again adds another similar arrow to the map, up to a maximum of four. These arrows persist until the server is stopped and restarted: this removes all green markers from all maps, except those are in item frames, which retain one marker at their current location.