Other mistake: When Harry, Ron and Hermione rush to Hagrid after the end of the year exams, and Harry is saying something that ends with, "Why didn't I see it before?", Hermione is mouthing part of that line. [Emma Watson did admit she learned Dan and Rupert's lines as well as her own and found herself accidentally mouthing them.] (01:50:40)
Other mistake: When Harry receives his first letter in the mail, Dudley snatches it from him before he has a chance to open it. Then he gives it to his father (Uncle Vernon), and Uncle Vernon says "Who'd be writing to you?" If you watch Dudley carefully, you can see him mouth what Uncle Vernon is saying. (00:08:54)
Other mistake: During the Quidditch match, when Hermione and Ron are talking, they mouth each other's lines. (01:20:45)
Other mistake: In the Quidditch scene when Harry and the Slytherin seeker are chasing the snitch and are trying to bump each other off course you can see Hogwarts in the background. They pass Hogwarts twice while going the same direction. (01:22:05)
Other mistake: In the scene where Professor Quirrell removes his headwrap to reveal the concealed Voldemort, Quirrell is obviously bald. However, if you carefully watch the scene with the troll, Quirell's sideburns are present after he shudders as the troll exhales, as they are in a couple of other shots. (01:10:43)
Suggested correction: The incident with the mountain troll took place on Halloween. The incident with Quirrell took place later in June. That is plenty of time for Quirrell to shave his head. Makes sense that he would as, I mean, I would rather shave my head if there was a guy on the back of it! Then I wouldn't have to worry about bumping his nose and him getting mad at me while using a comb. To be a mistake, we would need to see him with hair right before he is bald.
Other mistake: During the Quidditch match, Hermione looks in her binoculars up to where Harry is. If you look at the reflection in the binoculars you can see Harry flailing around. She then looks over at Snape, but when we see the reflection in the binoculars we still see Harry, as if she were looking up towards him. (01:20:40)
Other mistake: When Neville flies away but falls off it is obviously animated. When he falls behind the crowd of students they are covering up Matthew Lewis, the actor who plays Neville, but the place where Lewis and the animated Neville fell are different. (00:54:45)
Other mistake: During Neville's ill-fated flying lesson, as he approaches the statue from behind, we see that the statue is placed atop a round turret with alternating levels of bricks around the top of the turret. Neville's robe then snags on the spear of the statue. When we see the front of the statue as Neville falls, the statue is now standing atop a flat, level section of wall. (00:56:55)
Other mistake: When Harry, Ron, and Hermione go after the Philosopher's Stone, the harp stops playing. They look up at the dog, but its shadow is cast on the ceiling above them as well as on top of them. This shows there were lights behind the 3. (01:56:00)
Other mistake: In the scene where Ron and Harry are on the train to Hogwarts, the window to the compartment is open. We know this because the chocolate frog jumps out the window and is swept away by a pretty strong wind. Since the window is indeed open, shouldn't there be a visible breeze thoughout the compartment? (00:35:50)
Other mistake: In the scene near the end of the movie where Harry boards Hogwarts Express to go home, Hagrid stands on the platform and waves goodbye. He is wearing a coat and looks huge, as usual, but you can see when he waves, that his hand seems rather small compared to the rest of his huge frame. (02:23:15)
Other mistake: While Harry and his classmates are on their way up to Gryffindor Tower right after the Sorting, Neville reacts with astonishment to a portrait moving. However, we learn in later films that Neville was raised in a magical household (by his grandmother), so he should have been completely accustomed to seeing pictures move. (00:46:30)
Suggested correction: Not every magic household has moving pictures in the house.
No, but being raised in the magical world he will have come across moving portraits. A good example (tho not explained until book 5) is at St Mungo's. He visits his parents regularly. The hospital has portraits there that would move. Thus seeing the one move at Hogwarts shouldn't have startled him.
I am now doubting it's Neville who is saying it. Can't be sure it's his voice. It can also be he is mentioning they are portraits, not photographs that are moving. Maybe moving paintings are rarer.
Other mistake: Near the beginning, when the Dursleys' house begins shaking, none of the objects fall nor do the curtains shake. (00:11:00)
Other mistake: While Harry is sitting on the troll's shoulders, the troll grabs Harry's right leg and pulls him off, but in the next shot the troll now has Harry hanging upside-down by his left leg. (01:11:10)
Other mistake: Albus Dumbledore's name is spelled incorrectly on his card (after the chocolate frog escapes the container). It's spelled with an "E." (00:36:00)