What is internet-margin rule?

Girls tend to photoshop their pictures on the internet all of the time. When a boy is talking to a girl e.g via MSN and she sends him a picture of herself looking stunning, the boy must never forget the internet-margin rule. Because in reality this girl can be very unattractive. To avoid awkard situations the boy must picture her as atleast 20 to 30% uglier then on the pics.