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.
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)
Answer: "Hush, Hush, Hush" Paula Cole.