I think it has to do with how to get perfect pixel in illustrator. If you just draw a line even if you have your rulers set to pixel you will get anti-aliasing once you render it in for instance photoshop. So what you do is that you offset it in points as far as I can remember by .5pt that way PS will render it nicely.<p>Having said that I still don't know why someone thought of this to be HN worthy it's a rather old problem with a rather old solution.