I 'm using the jquery .offset().top to build a fixed menu on my website and it works absolutely perfect but ONLY when the user look at the top of the page. If you try to scroll the body down to the middle and then try to click at the left links of the menu the scroll has strange behavior and doesnt display the correct anchors anymore or even worst stops to work. Why is that? What i 'm doing wrong?

HERE IS MY JSFIDDLE