Continuity mistake: In the scene where William visits Anna on the set of her period film and they have a discussion near the trailers, the same man pushing a trolley is in not one but three cuts back to Anna.
Continuity mistake: In the scene just before Anna goes into the bookshop with the painting there is an outside shot of the building. In front of the school you can see the woman kneeling down in front of a child but also if you look through the window and door of the shop you can see Will walking in wearing a blue shirt. In the very next scene he is sitting at his desk wearing a pink shirt. (01:39:15)
Continuity mistake: When Hugh character takes Julia Robert's character back to his flat, after the orange juice incident. She isn't wearing her sunglasses in the next shot she leaves the building and she is wearing her sunglasses again. (00:16:30)
Continuity mistake: In the scene where Julia Robert's character first goes to Hugh Grant's character's flat, there's a chalkboard that's telling Spike to clean up. It's quite small writing, but in a close-up of Hugh Grant when he's directing her upstairs it's clearly larger. It then goes small again until she comes downstairs, when it goes large and stays that way. (00:12:10)
Continuity mistake: Anyone familiar with Notting Hill will know that the rooftop terrace scenes with Spike and William and later with William and Anna, were not remotely in the same neighbourhood as William's flat with the infamous Blue Door. The rooftop scenes were filmed most likely on rooftop between Ladbroke Grove and Stanley Gardens, while the flat with the Blue Door is located on Westbourne Park Road.
Audio problem: Anna is at Will's place to take refuge from the press. In the morning he opens the door, unaware of any trouble, and faces a yelling and hooting crowd of reporters. Then he shuts the door, and you don't hear a thing, although the door looks anything but soundproof. (01:18:55)
Continuity mistake: In the scene just after Anna opens the door and all the photographers are outside, Spike walks to the front door in his grey underwear. Just before he opens the door the underwear is covering only one butt cheek (his left). The next shot outside the house the underwear is adjusted and covers both butt cheeks but then when he enters the house and is checking himself out in the mirror, his butt cheek is exposed again.
Continuity mistake: The spring closing the front door when Anna first enters the flat (orange juice scene) is upside down when she next enters the flat (escaping the journalists).
Other mistake: The two cappucinos that Will brings back to the bookshop, which are then consumed during conversation, are obviously empty cups. The supposedly hot drinks are gone within seconds with no residue on the drinkers' faces.