Factual error: When Javert arrives in Paris to inform the Prefect that he has found Valjean, the government building displays the French Tricolour. This part of the film is set in 1823, during the Bourbon Restoration, so the flag should be the white, Bourbon flag.
Revealing mistake: One of the very last clips of the movie - one showing the barricade with a lot of flags - runs backwards. You can tell from the way the flags wave.
Continuity mistake: In the scene where Fantine is dying, she asks Jean Valjean to give a necklace to Cosette. There is a closeup of Fantine's head and neck and Valjean's hands enter the shot and begin to remove the necklace. A moment later she begins to cough and there is a cut to a two-shot of the pair from a few feet away. Valjean's hands are nowhere near her neck in the second shot.
Factual error: In the chapel sequence in which several young women are making their religious professions, the priest mispronounces the words "caelis," "sanctificetur," and "caelo." In the norms of ecclesiastical Latin the letter "c" when followed by the vowel "e" or the dipthong "ae" is always pronounced as the English "ch."