Continuity mistake: When the dog jumps in the back of the cab, he gets in the right side and Robbie is nowhere to be seen. It cuts away very briefly, and when it cuts back suddenly Robbie is very much on the right side of the seat and the dog is on the left- not enough time for them to have moved and settled in.
Continuity mistake: Right after JoBeth Williams and Craig T Nelson joke with Dr. Lesh about not showing the tapes of their haunting on "60 Minutes" or "That's Incredible", JoBeth walks to the table with Dr. Lesh's flask in her hand. As she walks from the sink, there's a silver cap on it. When she gets to the table, the cap is gone. She couldn't have removed it out of sight, she had a coffee cup in her other hand.
Continuity mistake: A few seconds before Robbie looks at his clown toy, you can see a Rubik's cube near his head. When the camera angle changes, the cube is gone.