如何使用Phonegap在iPhone应用程序的jquery mobile中设置固定位置背景图像

I am doing a iPhone app using Phonegap & also using jquery mobile. I want to set background image for data-role=page div. In this height of page is equal to screen & hence background is set to size of screen. But the page content length is much greater than screen & hence gray background is seen after image completes. My question is whether there is a way so that we can keep the background image fixed & scroll or move only content of page & not background image. Just to mention I have tried I am doing a iPhone app using Phonegap & also u