Revealing mistake: When Gabriel Noone goes to see "Peter", he arrives in rural Wisconsin, looks out of the window of his car, and sees a mountain in the distance. There are no mountains in Wisconsin.
Visible crew/equipment: When the girl is bleeding to death in the bathroom you can see a reflection of a camera in the sinks and cabinets.
Continuity mistake: When Ernie lifts the bike, he picks it up by the top wheel. When he is shown carrying the bike a second later, he is holding it by the lower bar.
Revealing mistake: When Zoe is getting killed she is spitting out blood from her mouth. Everything is ok with that, except she spits some of the blood on the camera right before she is thrown over the balcony.
Plot hole: The Death Note that Misa brings to L headquarters is supposed to be fake, but when Light touches it he can see the Shinigami Ryuk.
Suggested correction: Light saw Ryuk after he tried writing a name down in the piece of the notebook hidden in his watch. Since he touched that piece, it makes perfect sense he would see Ryuk as that piece was originally part of Ryuk's death note and wasn't swapped by L.
Continuity mistake: At the garden party, when Scarlett Johansson is sitting on the bench and talking, her hair is alternately tucked in and then on the outside of the sideframe of her glasses.
Continuity mistake: When we see Tully dead for the second time, the dirt patterned on his face is different from the pattern seen previously in the film.
Continuity mistake: Close to the beginning of the film, when Rachael and Brian are speaking at the desk where Rachael has been typing, between shots, a pencil appears next to her watch. This change happens right before Rachael says "I couldn't have done any of this without you".
Audio problem: [Blu-ray] When Mandy goes to wake up Red and Chloe, she says: "Hey! Hey, we need to get up, OK? Come on." The last two words were missed from the overdub, are not heard and are also missing from the subtitles. (01:08:15)
Revealing mistake: The infant baby was computer animated in every scene in which the face appeared. Even the feet were obviously touched up by computer in the hallway scene. The lighting isn't quite right, the skin texture isn't quite right, and the child's face is just too animated.
Continuity mistake: When Sue is talking to Mr. K, the phone rings four times before Mr. K answers it. But when Sue watches this scene on the cinema screen later, Mr. K answers the call after two rings.
Other mistake: François Cluzet and Marie-Josée Croze are husband and wife who grew up together and have been in love with each other since they were kids. They are shown in flashback scenes when they are kids as obviously being the same age. Yet it is obvious to the viewer that Cluzet is at least a generation older than Croze (15 years to be exact when I checked on IMDB.com) in the time that the actual story takes place in the present.