Continuity mistake: In the scene where Watson and Adler are laying out the map, they place two objects on the map to hold it down. In the very next clip where it shows Holmes talking, you see Watson and Adler placing those same objects on the map.
Continuity mistake: At the graveyard scene, when Holmes borrows Lestrade's pen you can see that he has unbuttoned cuffs, and a pair of cuffs underneath. When he takes off his hat and scratches his head in the very next frame, he has just bare skin under his unbuttoned cuffs.
Continuity mistake: When Holmes and Watson get off the boat onto land, they wade through water for a short distance. But in the next shot when they're inside, neither of them have wet clothes.
Continuity mistake: In the scene where Watson is moving his things out of the room and Holmes is examining a body, Holmes walks and goes to get a book once he returns, and Watson says "it will probably be a factory by the river" when the camera cuts back to Holmes one side of his shirt collar is down, although both sides were popped just seconds before, and seconds later the collar goes back to being popped. (01:16:45)
Continuity mistake: In the scene where Holmes is jumping from the office in the Houses of Parliament, the camera shot from the inside of the office as he jumps out of the window shows that his body is not fully out of the window as he falls down (his legs are still in the room). However, the view outside of Parliament shows Holmes jump clear of the window before he descends to the river. (01:38:45)
Continuity mistake: At the end of the film, in the bridge confrontation between Holmes, Blackwood and Irene Adler, Lord Blackwood forces Adler to the edge of a precipitous (and deadly) fall into the Thames. There is even a perspective shot, looking straight down, of her heels teetering on the edge and nothing between her and the river except two sailboats far below. There are obviously no scaffolds or other means of obstructing her fall in this shot. It's a dead drop. Then Blackwood shoves her straight backwards over the edge. But, when Holmes looks over moments later, Irene Adler is safe and sound on a convenient bit of scaffolding that magically appeared just a few feet below.
Continuity mistake: When Irene wakes up at the end and says 'I've never woken up in handcuffs before,' her lips have a light pinkish sort of color on them. Then she sits up and her lips have a dark red color on them. Quite a feat, putting on lipstick with your hands cuffed behind you.
Continuity mistake: As Holmes and Watson walk down a street after they've seen Blackwood's grave, we can see a man walking behind them, carrying something over his head. As the shot changes we see him passing them on the left side of Holmes. However when the shot changes again (Holmes says "Inevitably one begins to twist facts.") the man is turning right, behind Watson. (00:41:25)
Continuity mistake: When Irene Adler turns up at Holmes' apartment, Holmes lifts her necklace and we see the Maharaja's diamond hanging off it. When Watson asks Holmes to explain why he jumped through the window after her, when she leaves, we see another shot of her necklace, meant to be the same shot as before. But in the first shot, the diamond is hanging slightly to the left, and in the second, the diamond is perfectly centred.
Continuity mistake: When the big guy runs up to slipway 5 he passes a group of men and a horse in front of the door. When he opens it the camera is in front of him and behind him is a group of men and a horse and a wall and piles of crates that are nearly touching the horse - these have appeared from nowhere.