Continuity mistake: After Jack has escaped from the island where he was going to be burned, the makeup on his face (the eyes) changes between scenes. The makeup has faded quite considerably when he first boards the Black Pearl then in a later scene the makeup is neater and clearer. (00:42:30)
Continuity mistake: After Jack explains the legend of Davy Jones to Elizabeth, and they have found their heading, Elizabeth's braid is going down her back. When Jack points Elizabeth toward the ship her braid is now on her right shoulder. She doesn't move her head and there is not enough time for her to move it herself. (01:17:00)
Continuity mistake: When bound Jack begins his escape, he happens upon a young cannibal boy holding utensils, whose face and body are painted. A bit later, on the beach, the paint differs greatly - note the lines, etc. (00:37:55)
Revealing mistake: On the beach during the sword fight after the chest is found, in one overhead shot it shows the three men are casting shadows in different directions, revealing the presence of on-set lighting. (01:43:50)
Factual error: When Jack shoots at the hanging barrels of gunpower and rum, in the final battle with the Kraken, he fires a ball (presumably lead) as seen in the slow motion. However this would not cause an explosion as shown. There wouldn't be a spark for ignition. (02:05:00)
Continuity mistake: When Jack "intuitively" inquires about Elizabeth's feelings, the dangling beads in his hair are over his dreadlocks, near his shoulder. Next close-up they're tucked under his hair. This type of thing - with all the do-dads in Jack's hair - occurs numerous times throughout the film. (01:35:20)
Continuity mistake: When Tia Dalma asks, "Would you sail to the ends of the earth to fetch back witty Jack and his precious Pearl?" her lips are only partially covered in black. However, when she says, "Then you will need a captain who knows those waters," her lips are covered entirely in black.
Continuity mistake: After the ship with the "bride spirit" is attacked by the Kraken, Will ends up underwater, and when he surfaces his hair is soaked and slicked back, as he climbs on the ship's debris. However, in the next shot, his hair is parted, stringy and falling to the front. (01:33:50)
Continuity mistake: After arresting Will and Elizabeth, when Cutler Beckett holds up Norrington's arrest note, the way the paper is folded and how he holds it differs between shots. (00:03:20)
Continuity mistake: While Elizabeth listens as Captain Bellamy tells his crew that the stowaway is likely naked, she drops the paint brush into the pail. When it cuts to the close-up, the paint brush handle rests much higher in the pail. (00:46:05)
Continuity mistake: At Tia Dalma's, when Will tosses the knife at the tabletop, there is a tall slim candle beside his right hand. However, in the next shot when Tia Dalma says, "Against the cold and the sorrow," the candle beside his right hand is now very short, though no time has passed. (This doesn't refer to the short, wide candle in both shots.)
Other mistake: When Jack and Norrington duel on the stairway of the old church (before Will joins the fun), just as Norrington grabs hold of the key with his left hand, a band-aid is visible on Norrington's thumb. (01:50:00)
Continuity mistake: When Norrington runs with the chest, he falls and his sword ends up beside shell-head when he also falls. After the quick shot of his headless body running with the chest, in the next close-up the sword is farther away from shell-head, just before his crab-like legs appear. (01:54:40)
Continuity mistake: After Bootstrap gives Jack the black mark, when Gibbs shouts, "Back to your stations, the lot o'ya," the cloth round his neck changes position, depending on camera angle. (00:17:00)
Continuity mistake: The actual position of the burning word "Tortuga" differs between the first shot as it begins to burn on deck and from the close-up of the flames. (01:04:15)
Continuity mistake: When Jack beheads the pirate, the chest lands between certain plants, but when he kneels beside the chest to unlock it, the plants differ - despite the angle of the camera. (01:50:30)
Continuity mistake: Aboard the Pearl, when Elizabeth reaches for the gun at the top of the stairs, her hand is clean as Jack appears. As she hugs Jack's leg, her hand/fingernails are black and filthy. (02:04:10)
Revealing mistake: When Jack, the monkey, runs off with Ragetti's false wooden eye, the pirate's eye socket does not look empty in specific shots, only covered by a contact lens. (00:41:10)
Factual error: In the opening scenes of the film, the audience finds that Tom Hollander has warrants for the arrests of Orlando Bloom and Keira Knightley for a number of charges, one of which in conspiracy. However, while conspiracy is considered a distinct charge under American law and jurisprudence, this is not nor was it the case under British law. According to the principles of British common law and jurisprudence, conspiracy to commit a crime is legally identical to the commission of said crime (e.g., conspiracy to commit treason is considered treason). (00:03:20)
Continuity mistake: At the edge of the cliff, in the first overhead shot, when the four men lift the coffin its "head" side is nearest the water. However, in the next shot the "foot" side is nearest, before they throw it in the water. (00:05:30)
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.