Continuity mistake: When Norman Osbourne is in the tank, there is a close up on him at one point, and he has an expression of despair and fear on his face. But in the next shot, a wide one showing the green gas filling the chamber, Norman has a completely different look on his face. (00:16:35)
Other mistake: The scene in the hospital is supposed to take place in winter, since it's after Thanksgiving, but the trees visible outside the window are in bloom. (01:32:25)
Visible crew/equipment: At Thanksgiving dinner, when Aunt May looks outside when she sees something, the reflection on her glasses shows what appears to be a green screen. (01:26:00)
Audio problem: Immediately when Peter and Harry walk into the room with the genetically engineered spiders, Peter says something like "Wow, that's amazing." His mouth does not move. (00:06:35)
Continuity mistake: In the end sequence between Peter and Mary Jane by Uncle Ben's grave, as the camera switches perspectives, there's a wayward lock of Peter's hair that disappears then reappears in different shots. (01:49:20)
Continuity mistake: When fighting the Carjacker, Peter dropkicks him using a pipe. When Peter does this, the Carjacker has his cap on as he moves out of frame. When moving into the next shot, the Carjacker no longer has his hat, which now disappeared into thin air, never to be seen again. (00:47:50)
Continuity mistake: In the Thanksgiving scene where they are waiting for Peter to arrive, Peter swings onto the side of the building and drops down onto the balcony of his bedroom. To soften the drop onto the balcony, he bends his knees. When he unbends them and takes off his mask (the next shot) he is in the center of his bedroom, not on the balcony where he landed in the shot previous. (01:25:50)
Continuity mistake: When Peter is taking out the trash, and MJ walks out and says, "Were you listening to that?". Watch Peter as he turns around to look at MJ twice. (00:27:40)
Continuity mistake: When Peter is talking to Mary Jane in front of the diner, a light maroon colored caddy passes by twice. The first time when she says she just got off a job, the second when the boss shouts at her. Sure, there could be two cars the same color in NY, but with the same driver...? (00:55:15)
Continuity mistake: When Peter catches up with Mary Jane outside the cafe, there is a motorcycle that passes by Mary Jane. When the camera cuts back to Peter there is no evidence of a motorcycle passing, not even a sound. (00:55:40)
Continuity mistake: At the end of the film, when they are at Norman Osborn's funeral, just before and after they kiss, Peter's hair keeps changing.
Continuity mistake: When Spider-Man finishes beating up the thugs and after Mary Jane kisses Spider-Man, when you watch the one shot from the side, Mary Jane only starts to put his mask back on. But when the angle changes, Spider-Man's mask is properly on when Mary Jane didn't even move her hands. (01:21:40)
Continuity mistake: At the beginning of the film when the class is being shown around the museum, the class moves on. In the background a black guy with a red t-shirt and black overalls walks away. In the following shot of Peter's face, the same black guy walks off again. (00:08:45)
Continuity mistake: After the wrestling match when Peter goes to collect his money only to receive 100 bucks, he argues with the guy, if you watch, the guys hand is on the money bills, yet in the following shot, his right arm as well as his hand are on the desk. (00:40:00)
Continuity mistake: In the lab experiment scene, Osborn's pulse is tracked on a computer screen, which shows his pulse numerically, and graphically, and emits a 'beep' with each beat. When his pulse accelerates, the meter races higher, but the beeps, though fast, sound consistently at the same rate. (00:16:55)
Continuity mistake: After Mary Jane slips while carrying the food tray and the food is thrown into the air, the shot facing the ceiling showing the food falling shows the bowl of jello to hit first and the apple to hit last, while the next shot shows Peter catching the apple first and the bowl of jello last. (00:21:10)
Continuity mistake: When Jameson is talking to his coworker in his office, the other man holds out a paper. From one angle it's in his left hand, and from another angle it's in his right.
Continuity mistake: In the museum, when Flash is messing with MJ, MJ looks at Peter as he moves ahead of her, yet in the following shot they are shoulder to shoulder. (00:06:30)
Continuity mistake: When Peter runs out of school just after he beat up Flash, he runs into an alley and looks at his hand which is at waist level, then it cuts to a different view, his hand is now at neck level and one of his fingers is pointing up, then the shot after his hand is back to waist level and all fingers are straight and pointing down. (00:24:20)
Continuity mistake: In the scene in Jameson's office after he throws his cigar out the window and the Goblin throws it back, when Jameson is looking at the cigar on his desk, he is sitting at an angle. Right before the Goblin crashes in, Jameson is sitting perfectly straight at the desk, with both hands on the desktop. (01:11:50)
Answer: Remember that Green Goblin (Norman Osborne) just found out that Peter Parker is Spider-Man. Aunt May's comment about everyone knows he loves Mary-Jane concerns him because he now realizes that Green Goblin might find/kidnap Mary-Jane just to lure Spider-Man into a fight. This is the basis for the whole reason he can't be with her, as he would be potentially putting her in harm's way all the time if they got together.
Jazetopher