Continuity mistake: Near the end of the film, between the time Carrie finishes her bath after the prom and the time her mother stabs her, the wetness of Carrie's hair changes from shot to shot. When she first puts on her nightgown, her hair is almost dry; later on, about when her mother says, "We'll pray," her hair is very damp; when her mother stabs her, her hair is almost dry again.
Continuity mistake: In the scene in the beginning of the movie when Carrie's mother puts her in her "praying room" the room is pitch black. When it cuts to an overhead shot of Carrie in the room, the room is lit either by a window or something else. This is before she lights a candle.
Continuity mistake: When the blood is poured over Carrie at the prom, it only covers her left side - hair, shoulder, arm, body. But in the next shot the blood is all over her, especially her hair. The blood on her face is strategically placed, so it isn't in her eyes or cover her too much.