Revealing mistake: When the Dilophosaurus spits at Nedry, you can see the smoke from the gun used to shoot the spit in his face, top left of screen. (01:10:50)
Revealing mistake: In the shot immediately following Ellie turning on the circuit breakers when the raptor attacks her, we see a light bulb touching its head. There is smoke appearing where the bulb is in contact with the raptors head, the power has been off for a while the bulb would not be that hot after being on for just a few seconds. (01:39:35)
Revealing mistake: The T-rex does not leave or make any footprints in the soft mud during the attack on the car.
Revealing mistake: During the whole scene of the T-Rex attacking the Explorers you see an illumination that moves from place to place. Sometimes the illumination is in the deep woods, and then it is behind the dinosaur when it is next to the vehicle. When the T-Rex first walks up and sniffs Tim and Lex's Explorer you can even see the light to the left of Rex's head. Since the power is out, no lights are on except the vehicle headlights and they aren't making that much light. Also, there is no moonlight since it is pouring with rain. (00:58:00 - 01:07:00)
Revealing mistake: When Alan and Tim climb down the tree to escape from the falling car, you can see cables along the bark of the tree below the car as it falls. (01:14:20)