When the baby dinosaur is born, one minute the robotic hand is there behind the egg as it's hatching, then in the reverse angle the hand's suddenly disappeared.
When Nedry is trying to escape, and his jeep gets stuck on the mud bank, the camera shows the road below him, and there's an arrow pointing straight ahead. A bit later, the camera shows it again, and the arrow's now pointing left.
In the scenes where there's a video link to the docks shown on computer, there's a bar moving along the bottom of the screen, showing us that it's actually a video that's just playing on the computer.
The satchel of money Nedry receives as a down payment for getting the embryos off the island vanishes from his arms as he looks at the false container of shaving cream. It vanishes mid-sentence; he had no time to put it down.
At the badlands, when Hammond's chopper has landed and Grant goes to the trailer to open the door, if you watch the hinges of the door, they're on one side then it cuts to the inside of the trailer and the hinges are on the other side.
When Lex and Tim are in the car and the T-rex is attacking them, at one point the T-rex smashes through the roof of the car and the clear roof falls through on top of Lex and Tim. The T-rex breaks it with his teeth, but in the next shot it's whole again.
Take note when the vehicle starts chasing Sam Neill and the kid down the tree. When it first starts to fall, it smashes a headlight and damages a foglight. In the next shot both lights are undamaged and operational.
When Tim, Lex and Dr. Grant are hiding in a large tree, a large dinosaur appears. They pull some branches off the tree and feed the dinosaur. However, when they first climb the tree, there is no foliage in the area at all.
During the scene where Dr. Grant and the children are forced to climb a fence to flee from an unseen dino, there's a brief side view of the fence that clearly shows that it isn't continuous - it is probably only about 75 feet wide.
When the T-Rex is knocking the car with Lex and Tim in it, he knocks it once, and then again making the Jeep flip over. If you watch that exact scene in slow motion, you can see a big wooden pot containing one of the fake trees for the set and a stage light.
When the T-Rex is approaching, the lawyer runs into the bathroom stall and the roll of toilet paper is mounted horizontally. After Ian runs towards the bathroom away from the T-rex, in the shot of the panicked lawyer as he shuts the door the toilet paper is now mounted vertically, but when the T-Rex knocks down the stall walls, leaving the lawyer sitting out in the open, it is again mounted horizontally.
When Grant and the children are up in the tree, as Tim is telling his jokes the camera pans out and we get a wider view. In this shot you can see that Grant's boots are spotlessly clean, which is highly unlikely given the muddy ground, wet environment and his activities over the past few hours.
When Tim is shocked off the fence as the power comes back on, the sparking effects are not where his hands are touching the wire but several inches away.
When the lawyer jumps out of the jeep (just before the T-Rex approaches) he leaves the jeep door open. In the next two shots the jeep door is closed, but when the T-Rex shows up, the boy moves to the door and closes it.
In the badlands segment of the film, after Ellie, Allan, and Hammond enter the trailer. Hammond decides to open the bottle of champagne that Ellie, and Allen were saving. Hammond begins to buff a couple of glasses with a towel that magically changes to a pink towel in the next shot.
When the two Explorers start off on the tour of the island and the vehicles reach the Dilophosaur exhibit, there is a shot of Lex, Tim and Gennaro, looking out their Explorer's passenger-side windows. Right above their heads, fastened directly above each window, are wind-screen covered microphones. Obviously placed there to pick up actor dialog, neither of these particular mikes are seen again before or after this shot.
When the Explorers are entering the park through the large wooden gate, during the overhead angle you can see that the perimeter fence isn't continuous.
Watch carefully the scene where the raptors enter the kitchen (that angle where you can see almost the whole kitchen while raptors are coming in from the far away door). As the first raptor enters the kitchen, you can see someone grabbing its tail to hold the puppet-thing steady.
When the T-Rex has a raptor in its mouth at the end, the raptor disappears completely from the T-Rex's mouth for one frame. It's just after it's picked up - the T-Rex swings it left, then right, and as it swings to its left again the raptor disappears. If you want to be even more precise, there's a slatted/stepped white bit above the door - the raptor disappears about 3 frames after its foot moves above that white bit.
See all the mistakes in Jurassic Park