Corrected entry: When Quasimodo's mother is running from Frollo, she stops at the Cathedral to beg sanctuary. She turns to see Frollo coming after her. When she does she is standing very close to the cathedral. When she turns to run again, she is instantly several feet away from the cathedral wall with no time to get there.
Correction: The sequence goes as follows: Mom bangs on the cathedral door; she turns and starts to move. Then Frollo emerges from the alley for several seconds. We cut back to mom, who is some distance from the door, but not so far that she couldn't have run there while we were seeing Frollo. She turns and runs away, Frollo charges up the stairs in pursuit. As she nears the stairs, Frollo grabs the bundle and kicks her, where she falls to her death. There is no "instantly several feet away."
Corrected entry: Phoebus claims he has been called home from the war. Problem is, France wasn't at war in 1482, and hadn't been since 1451.
Correction: The movie doesn't make the claim that it's 1482, though that's the setting of the novel. In any case, Phoebus claims that he had been recalled from "the wars" (plural). This could indicate that he was merely stationed somewhere that had recently seen battle (perhaps during the recent Burgundy Wars, which ended in 1476) and where a new skirmish could potentially break.
Corrected entry: In the scene that Frollo is speaking to Phoebus about the dregs of Paris and illustrating it by lifting a stone and revealing all those bugs underneath. He slams the stone back down crushing the bugs, but the stone was turned upside-down, even though the whole scene never loses sight of Frollo holding it, and he never turns it that way.
Correction: He doesn't turn the stone upside down, he just turns it sideways.
Corrected entry: In the film's opening it is stated that Frollo gave Quasimodo his name out of cruelty, and that it means "half full". Actually Quasimodo translates (roughly) into "in the manner of". In the book the name was given to the character because Frollo found him on Quasimodo Sunday.
Correction: Actually, it says "half-formed." "Quasi" means "as if," and "modo" means "a way of doing [anything]." Meaning, in this case, that Quasimodo looks as if he were only made in the way humans are made, not as though he is actually human. "Half-formed" actually describes this pretty well. Movie and book discrepancies are not valid mistakes at any rate.
Corrected entry: When Frollo shoves Quasimodo's mother backward on the steps of Notre Dame, she falls, hits her heads on a step, and dies. However, if she hit the ground hard enough to get killed, her head would have been cracked open and there would have been blood all over the place. When the Deacon comes out of the church and discovers her, he even chastises Frollo by saying (singing) "See there, the innocent blood you have spilt." The problem? No blood is visible at all. This is due to the fact that Disney will not show evidence of violence in their films, but it is still a mistake. It just doesn't feel right when the characters can see the blood and the audience can't.
Correction: Actually she broke her neck. Saying that blood has been spilt doesn't necessarily mean that someone bled, it means someone was killed.
Corrected entry: When Frollo locks the family inside the mill before setting fire to it, he bolts the door by using a spear as a cross bar on the outside. The door opens in and would not be blocked by the spear.
Correction: When Frollo locks the family in, you can see the door handle curves upward on the outside, so the spear is going across the handle and wall, not between the posts.