I think you have heard of about LightBox project that lets you overlay the images on the current page. It must be possible to do that action with ASP.NET AJAX and AjaxControlToolKit. Matt Berseth figured to use ModalPopupExtender control with Animation from AjaxControlToolKit and makes a usefull a new extender named as ModalPopupAnimationExtender. So you must see his post and his process for this extender. Click here to see his post. Well done Matt !