Chrome和Safari中的背景被推下来了

I used "320andup" in order to make my first real responsive website. I managed to have a perfect adaptive environment except only one thing. The background image in Chrome and Safari is pushed down 18px. I can't explain why. Only thing I know is that when i add in the body tag "background-attachment: fixed;" the problem is solved but when I scroll I get an ugly experience that I don't want to have. I also tried thisI used "320andup" in order to make my first rea