Continuity mistake: When leaving from the baseball scene, Emmett's jeep goes from being dirty on the sides with mud from the tires, to being clean.
Continuity mistake: During the hospital scene, when Edward is "sleeping," his head goes from from leaning on one shoulder to suddenly on the other shoulder in the very next shot. In the top shot there are 2 windows next to Edward's head, but the windows are not there in the next shot. Things on the table have moved too.
Continuity mistake: When Bella enters Biology class and talks to Eric about the prom, she starts to walk, then pauses to look across the room towards Edward. In this shot, the Armadillo is not on the shelf, only what looks like a peice of paper is hanging there. The Armadillo appears on the shelf only after she has sat down at her desk and Edward moves the microscope towards Bella saying, "Ladies first".
Continuity mistake: After Edward saves Bella from being crushed by the van, while he is holding her, Bella's hair is outside of her jacket covering up her hood. When the shot changes her hair is tucked beneath the jacket and the hood is visible. When the shot changes back, her hair is covering up her hood.
Continuity mistake: When the Cullens are in the garage preparing to take Bella to safety, Edward closes the trunk lid twice. First time is not so obvious because the camera is on Emmett and Rosalie, but the trunk closes on the right of the screen. Then it shows it closing again with it being the main shot.