Sorry about the lack of a picture

Have you ever noticed how the position of Harry's scar is different depending on what you're looking at?
In the movies, it's over his right eye. The book illustrations put it in the middle of his forehead. In both cases, it's vertical.
I have an old blanket on my bed. Quidditch, of course. Harry's scar, as depicted on the blanket, is in the middle of his forehead and horizontal.
I'd also like some explanation for it. (Please don't say that the books never saay exactly where it is.)