Revealing mistake: When Diane is pulled back from the front door near the end of the movie, they use a stunt double, as you can see the stunt person scramble off to the right after the real Diane lands behind the stairs.
Suggested correction: You're close. They did use a stunt double but you don't see the double "scrambling off." The stunt double is barefoot and the person you see clearing the shot is wearing shoes. Most likely a stage hand helping the stunt double with the landing.
Continuity mistake: When Carol Anne goes to the TV in the parents' bedroom the first time, the clock on the TV changes from 2:38, 2:58, 2:38 and then back to 2:53 with each camera angle change.
Other mistake: The night after burying the bird, a lightning strike projects an image of the tree outside onto the bedroom wall. However, the silhouette has nothing to do with the tree's shape.
Factual error: During the climax of the film, coffins from the cemetery below rise out of the ground. Only problem: they're rising vertically. Coffins are laid horizontally.