Revealing mistake: In the scene when the main character is in the library on the internet, she goes to a couple of websites. When the shot shows the URL up top, it is C:\windows98\mydocuments\etc.html. Instead of actually searching on the web they used a premade html page and accessed it from their computer.
Continuity mistake: Near the end of the film, on the train ride out of the Hive, Rain is quite close to becoming undead. When she speaks, we notice her teeth are still "movie-star white". However, a few shots later, when she becomes a zombie, she sort of hisses where you can see it has taken what couldn't have been more than a few mere minutes for her teeth to become brown and discolored. (01:21:00)
Other mistake: After Michael kills Laurie at the beginning, he hands the knife to the inmate with the clown mask. The next kill is the cameraman for which he uses the tripod ends. A few scenes later they show Michael standing holding a knife with fresh blood on it. He hasn't killed anybody with this knife yet so where did the blood come from?
Continuity mistake: In the scene where the townspeople are fleeing to the mall there is a shot of the Deputy driving the car. You can see the top left hand corner of the windshield is covered in green goo, but when you see them parking the windscreen is completely clean. (01:03:35)
Other mistake: Towards the end of the film, after Snipes beats up of a lot of vampires, Whistler throws Blade's sunglasses to him. They show him throw them in one shot, then in the next shot they show Snipes catching them. But look in the background at Whistler, he doesn't have the glasses, but is moving his arm like he is throwing them. The glasses must have been computer animated, and bad editing contributed to this mistake. (01:37:34)
Visible crew/equipment: Watch the scene where Frank gets killed. In the last shot of this scene, we see a soldier standing over the dead body. Keep an eye on the right side of the screen as the camera slowly moves away and you should see one of the cameras and a cameraman on the ground next to a large metal object.
Factual error: When May cuts her eye out with the scissors at the end of the movie, the fake eyeball used for the effect is perfectly round. A human eyeball is far from being perfectly round.
Revealing mistake: When the megalodon attacks the yacht the party goers jump off the yacht, and some of them reach the large round safety raft. To the raft's right, there is a visible yellow line attached to it so it doesn't drift away for the shots.
Factual error: The rifles the British soldiers carried in the film were Lee Enfield rifle No. 4's, these did not go into production until WW2. They should have been using an earlier version of the Lee Enfield rifle.
Factual error: When Ellen gets married in 1907 she is 20, but when she disappears in 1950 she is 70.
Continuity mistake: At the beginning of the film, the little boy has big brown eyes. 19 years later, when the boy is shown as an adult in the diner, he has big blue eyes.
Plot hole: The dead young girl who wears white has hemophilia (uncontrollable bleeding), and her mother states that she's scared of all sharp metal objects (scissors, etc.), yet she goes to play in an old abandoned steel mill all the time.