When Hannah enters Danny's house a gust of wind messes up her hair, but in the next shot her hair is neat again.
Hannah is sitting on her bed writing a letter on her laptop. She then gets up and puts the laptop down on the bed - however the screen is blank and she didn't turn the laptop off.
When Danny falls into the garbage cans, the mask on the stuntman's face becomes undone and reveals him.
When Hannah is narrating while typing a letter to her friend, the camera changes to her using the keyboard with her index fingers, and she is obviously pressing the Y,U,G,H,J keys over and over.
In the beginning, on her music certificate, her name is spelled "Hanna". Later, on the note from her family it is spelled "Hannah."