Continuity mistake: When Norrington, Jack and Will bang away at each other on the beach, in the shot facing Elizabeth as she puts her hat back on, behind her Ragetti runs ahead of Pintel (3-4 ft) as they steal the chest. Next shot, it is Pintel in the lead as they run off. (01:49:00)
Continuity mistake: After Will slides down the sail, just as he grabs hold of the mast line, the cut sail is only tied down at its corners. After he puts the knife in his mouth, the sail is also tied down directly under the cut. (01:36:10)
Continuity mistake: When the cannibal walks across the bridge and sees some prisoners fall to their death and the others escaping, there is a long stick, which has a black design on it, threaded through his lip. When he arrives back at Jack's roasting, the stick's design is very different. (00:36:10)
Continuity mistake: When Will, Gibbs and the rest are in the ball cage and escaping the cannibals, they roll down a hill and hit a tree, which they then roll up. This would be impossible unless the weight is evenly balanced throughout the ball completely. (00:37:50)
Continuity mistake: When Jack blasts the bird pecking on the coffin, the wood debris differs between shots. As his gun-toting hand still pokes through the hole, there is attached wood debris sticking up 90° at the sides of the hole that was not in the previous shot. (00:06:10)
Continuity mistake: When Elizabeth sits on deck and points out the burning word Tortuga, the wound lines beside her change position between the shot facing her and the next shot, behind her. (01:04:30)
Continuity mistake: Aboard the Pearl, after Will orders the rum to be loaded, and Gibbs responds, "Aye, the rum too," the cloth round Gibbs's neck has the loop to his right, but in previous and following shots it's actually "tied" round his neck the opposite way, with the loop to his left. (02:00:00)
Continuity mistake: After the Flying Dutchman's attack on the Pearl, when the Kraken attacks the Pearl, one of its tentacles comes through the captain's stateroom stern windows, which has considerable damage - notably the left window and part of the wall are completely gone. When Gibbs says, "Abandon ship or abandon hope," the stern windows are actually more intact - especially the left window/wall. (02:03:50)
Continuity mistake: When Cutler Beckett shows Will the Letter of Marque, the seal beside King George's signature is seen. Later, while Elizabeth points the gun at Beckett, he places his own seal below, and the shape of King George's seal is entirely different now. (00:11:20)
Continuity mistake: After the cage of bones falls into the water, Cotton reaches up out of the water to open the broken cage, but in the next shot he is still under the water, behind Marty. (00:40:45)
Visible crew/equipment: While Norrington and Will begin their duel, Jack walks away and promptly falls into the open grave. In the shot of Jack from within the grave, the imprint of a modern, flat bottom trainer/sneaker sole can be seen on the dirt wall (yes, wall) to Jack's left. It is not the imprint of a shoe of the time period. (01:48:00)
Continuity mistake: In the scene where Will visits Elizabeth in jail, she is rubbing his chin in most of the shots but in one shot her hand is suddenly down and then it goes back up again in the next shot. (00:18:40)
Revealing mistake: The crow pecking on the floating coffin Jack is hiding in has a modern-day identification band on its leg. (00:05:50)
Continuity mistake: When Pintel, Ragetti and the dog are in the boat, the corner of Pintel's collar is folded up when he says, "Aint that right, poochy?" and also when the dog jumps into the water, yet, it is folded down in the other shots. (00:29:15)
Continuity mistake: During the dice game aboard the Flying Dutchman, when Will challenges Davy Jones, the cloth with the key drawing is folded and positioned differently between shots. (01:21:00)
Continuity mistake: When Elizabeth, Will and the rest watch from the long boat, as the Kraken takes down the Pearl with Jack aboard, in the shot facing the Pearl Cotton sits directly behind Will, but in the shot facing the long boat Pintel sits behind Will. (02:14:55)
Continuity mistake: After Will challenges Jones he is given five dice - one being considerably smaller than the other four. However, when Will looks under his cup during the game, all five dice are of similar size. (01:22:00)
Continuity mistake: When Jack shoots a hole in the casket killing the bird, the amount of feathers on the casket differ between the shots. (00:06:00)
Continuity mistake: After Jack takes the heart out of the chest he hurriedly closes its lid, the locks engage, and the key's end remains in the horizontal position when Jack runs off. However, when Pintel and Ragetti grab the chest the key's circular end is now vertical - the key does not turn itself. (01:51:00)
Continuity mistake: When Elizabeth questions Jack about his "broken" compass as they stand on deck, her left arm rests on the deck rail and changes position back and forth between shots. (01:36:30)
Answer: The jar was to put Davy Jones heart in. He can't touch dirt ever again since he failed to keep up his duties which means he wouldn't be able to get his heart back.