Continuity mistake: When Shaun goes to the newsagents after the dead rise, he gets a drink out of the fridge, which has blood-stained hand prints on. He slips on what we assume is blood as he walks away, yet on the way in and as he leaves the shop you can see behind him that there is no blood or any other liquid on the floor.
Continuity mistake: After Ed and Shaun make the plan to save everyone, we see the close-up shot of the TV where the announcer is saying that nobody should try and save their friends and family. If you look at Shaun, you see the handle end of the cricket bat in his right hand, and he is facing the TV screen. In the shots immediately before and after that, Shaun is not only turned away from the TV, but the handle is in his left hand.
Continuity mistake: When Ed and Shaun use Pete's car, the rearview mirror changes its characteristics between shots. Things such as being large with perfect 90° angles to being smaller and having curvier edges or being attached to the black unit on the car ceiling to being attached to the windshield.
Continuity mistake: At the beginning of the film, when the camera pans across the road towards Shaun's house, the silver Renault badge on the hood of Pete's car is missing, but when Shaun goes to work that morning (Pete sits in the car), it's there. The badge disappears again later in the film.