Other mistake: When Spider-Man shoots a single web out of each arm to stop the train, in the shots of his reactions, you can see that he is holding many webs in each hand. Then when he shoots multiple webs to try and stop the train, he has the same amount of different webs as before. Obviously they didn't have footage of him just holding a single web, and used shots from later in the sequence.
Other mistake: When Spider-Man and Mary Jane are sweet-talking in the web, her hair blows around freely, whereas considering how sticky a spider web is, her hair should be sticking fast to it. Permanently. After all, the web cannot be sticky enough to hold her body, while not being sticky enough to glue her hair.Sereenie