Continuity mistake: There are two external White House shots in the film. The second is a still shot, and should take place at least a few days after the first. However, it is a frame from the earlier shot, with the same person standing in the same spot on the lawn.
Continuity mistake: Clark and Lois are undercover in a hotel in Niagara Falls investigating a Honeymoon scam. There is a scene where Clark is removing money from his pocket to tip a porter. You can plainly see that some of the money is falling on the ground. In the next scene the porter walks away with his tip and the falling money has disappeared.
Continuity mistake: In the opening scene where the three villains destroy the energy crystal and the lights go dark and the rings descend upon them, the light that surrounds them is shown coming down from the ceiling. But, when the dome opens, the light surrounding them shines up from the floor. (As also seen in Superman: The Movie.)