Continuity mistake: In the hospital, after the 'almost' car crash when Edward saves Bella, she has a blood pressure cuff on her arm. You can see the nurse take it off. She has it off for a while, but then it reappears on her arm in one shot, just as her dad says "you can kiss your licence goodbye".
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 Bella enters the biology classroom and Edward has finally returned, as she walks over to her desk the large book sitting on the edge repositions itself from sitting horizontally to vertically between shots. The bit of paper above it also moves closer to the edge.