I have a ModalPopupExtender within a ContentPlaceHolder. The position on the ContentPlaceHolder within a masterpage is aligned about 100px left and 100px from the top.

My problem is when the ModalPopupExtender is fired, the background position is also position at 100, 100 rather than 0,0 and it makes my page scroll. I have tried various methods within the modalBackground css to position it absolutly with no success, and also placing the ModalPopupExtender and Panel in a div, again with no success.

Can someone point me in the right direction of how I can fix this?

Thanks