Continuity: The rope barriers along the ground leading to the desk in suite 1300.
Continuity: Pennants at gas station disappear and reappear between shots.
Revealing mistakes: Neal's car is a BMW e36 3-series convertible. When you see the burned-out car wreck near the end of the film, it is clearly visible that it is a e30, the older 3-series model. The wreck has no damages from the impact either.
Errors made by characters (possibly deliberate errors by the filmmakers): The website Neal calls up at the beginning of the movie is misspelled as "majordesicion.com" (the correct spelling being "decision", not "desicion").