Stop scrolling over edge of screen on iOS web apps?

Working on an iOS web app. The user can scroll the content of the page up a开发者_如何学Cnd down. However, is there a way to stop the screen from being dragged so far that the grey background becomes visible? This is replicable by opening any webpage in mobile safari and pulling the page down.

You can use a javascript library like pastrykit, or iScroll, to handle the scrolling instead of the default, similarly to how the mobile gmail webpage works, or the iPhone User Guide.