Continuity mistake: Watch when Sledge swings down from the balcony. In one quick shot, we see that there are two zombies in front of the store "Carlton's." When the shot changes to show Sledge landing, a third zombie has appeared from nowhere.
Continuity mistake: When Peter has just killed the child zombies and another with a messed face is in the doorway, we see Steven outside aiming a rifle and it is cloudy, dreary weather. Peter dives out the way and lands by a window and we see that it is now pitch black, then Roger steps in and shoots the zombie from outside and it's only just overcast.
Revealing mistake: When they lock the mall doors using the car, Peter is giving cover fire while the doors are being locked. Notice when the camera cuts to one of the shots from the scopes point of view he blows a zombie's head off and the blood splatters on the scope and is visible when the zombie drops.
Other mistake: During the truck scene, when zombies attack Roger the first time, as Peter shoots the zombie that Roger is fighting, he supports his M16 from its carrying handle, thus blocking the rear sight (which is located in said handle). He does this in several scenes throughout the movie, but in the truck scene accuracy is crucial.
Continuity mistake: Just after the raiders manage to get into the mall, one raider uses his sledgehammer to knock a zombie wearing a black t-shirt off his feet. 5 seconds later, the same zombie can be seen walking past the same raider.
Visible crew/equipment: When Peter is attacked coming out of a doorway (after he leaves the boiler room) he wrestles with two zombies. If you pay attention to the bottom of the screen, just before he pushes the zombies away, you can see the hands of a crew member come into the frame. They were probably making sure none of the zombie actors fell into the camera. 2003 Directors cut DVD version. (00:49:02)
Revealing mistake: When Stephen is trying to climb out the elevator after having been shot, a group of zombies attack him and the first zombie we see bites his leg. In this closeup of Stephen's leg being bitten, the tube that pumps out the blood is protruding out his trousers, obviously leading up his thigh.