Continuity: When we see the police officer checking the hit counter on an adult web site, the hit counter goes down from 1,739,986 to 1,739,944 a few seconds later.

Continuity: When Alex sees the cop hiding in the shower on the camera/web server towards the end, the hit counter is at the same level as it was earlier in the film (despite increasing steadily every second when we last saw it). Plus the mouse cursor is slowly moving up from "Camera 3" to "Camera 1", despite Alex not moving the mouse.

Revealing: When Alex drops the cigarette lighter to ignite the gas, you can see the flame is started from a different source, as it starts on the other side of the screen, a fair distance away from where the lighter landed.

Continuity: In the scene where Alex has just risen from the dead and escapes from the prison through the roof, there's a close up on him. His hair is much shorter in this shot then it was a few seconds ago. Then when he jumps down, his hair is longer again. This happens at least once more later in the film.

Plot hole: Kirsten Dunst refers to Alex wearing makeup several times, even though he is not wearing any at all, the marks on his face are the results of burns.

Revealing: When Alex is about to peel off his burned skin to reveal his iconic "crow" face, you can tell where the makeup switches from attached prosthetics to the fake "pull away" makeup.

Revealing: When Alex sees the arm in the burning rubble of the club, you can tell the arm is a prop because it is melting in spots, not burning up like real skin does.