Plot hole: When Phoebe and Cole are using the apple peel to find out her true love how does she not recognize that it is Cole? Even with the mask it's very clear that it is him.
Suggested correction: I was thinking the same, but it's possible she thought he was an ancestor/past life of Cole. When she visited her own past life, she recognized everyone there because of their "souls" so maybe she thought the same with him. Although you'd think they'd acknowledge that a little.
Revealing mistake: When Leo dropped the Grimlock potion, it was obviously fake when it hit the ground.
Continuity mistake: When Piper and Prue are standing in the bedroom with Charlotte, Prue's hand moves from covering her mouth in one shot, to being by her side in the next.
Continuity mistake: In the scene where Eva is teaching the sisters about ways to draw power on All Hallows Eve, she cuts an apple in half and puts a leaf over the seeds in the center. The leaf goes from small and only covering the center to bigger and covering more of the apple.
Sight Unseen - S3-E5
Factual error: When developing a photo it's first put into a developer chemical, which shows the picture up, then a stop, which stops it from developing anymore, then a fix which "sets" the photo. But in the basement, Prue puts the exposed photo into a tray with chemicals in it where it starts to develop, then into a second tray where it develops fully.
Sight Unseen - S3-E5
Continuity mistake: Cole goes to the manor, turns the AC on, knocks a lamp on the ground and opens a window, then shimmers up to the attic. When the sisters come home all the windows are open, but Cole opened only one downstairs.
Sight Unseen - S3-E5
Factual error: In the scene where the invisible demon is entering Cole's office, the courthouse shown before the elevator is a New York City courthouse, not San Fransisco. It's confirmed by the presence of a NYC Taxi.
Revealing mistake: When Prue is practising using her powers while astral projecting, when Phoebe walks away to go see her in the attack you can see the makeup they used in an attempt to hide her tattoo on the right side of her back. It looks as though she's been bruised there. (00:00:43)
Visible crew/equipment: After following the signs that lead to the demolition site, when Prue unlocks the chain on the door and enters the loft, the T-mark is visible on the floor at her feet. (00:03:45)
Continuity mistake: When Prue was talking with the shut-in and the security guard comes up and knocks on the door you can see the the chain is on the door. When he knocks again and says he is coming in and tries to open the door the chain is off.
Audio problem: When Prue is at the dentist, she grabs a guy and he says, "What, what did I do?" to his girlfriend, but his lips do not move.
Revealing mistake: At the end when Prue is fighting the demon you can tell she is holding on to her safety harness when she is in the air kicking him.
Continuity mistake: When Prue is in the basement with the priest she has curly hair, but when she comes upstairs to vanquish Vinceres it is completely straight, but she definitely didn't have time to straighten it.
Power Outage - S3-E7
Continuity mistake: When Cole drops Phoebe off at the manor after their date, Phoebe lowers her hand from Cole's face when they kiss, but then it's suddenly back up near his chin. (00:22:20)
Power Outage - S3-E7
Revealing mistake: When Astral Prue kicks Leo/Balthazar in the face during the training drill near the start of the episode, her foot misses his face yet he still reacts as if hit.
Power Outage - S3-E7
Revealing mistake: Alyssa's tattoo is visible when Phoebe leaves Cole's apartment after she fought with her sisters.
Power Outage - S3-E7
Continuity mistake: During the training drill, Piper fumbles for a knife on a table in front of her. In the shot of the table, she loses hold of the knife as she pulls her hand up, but when we cut to a long shot, it is back in her hand.
Sleuthing With the Enemy - S3-E8
Revealing mistake: When Cole / Belthazar grabs Phoebe to use her as a hostage, you can see, very obviously, that he doesn't pull her. Phoebe actually steps in front of him willingly, despite the look of fear on her face.
Sleuthing With the Enemy - S3-E8
Revealing mistake: When Phoebe throws the potion at Cole's coat, the vial doesn't shatter, even though it sounds like it. Watch closely, and you'll see the purple, unbroken vial bounce off the coat and away out of shot without any of the potion touching the coat.