function centerUpdatePanel() 
{
    var loadingPanelElement = document.getElementById("<%=rapLoading.ClientID%>");
    centerElementOnScreen(loadingPanelElement);
}

function centerElementOnScreen(element) 
{
    var scrollTop = document.body.scrollTop;
    var scrollLeft = document.body.scrollLeft;
    var viewPortHeight = document.body.clientHeight;
    var viewPortWidth = document.body.clientWidth;

    if (document.compatMode == "CSS1Compat") 
    {
        viewPortHeight = document.documentElement.clientHeight;
        viewPortWidth = document.documentElement.clientWidth;
        scrollTop = document.documentElement.scrollTop;
        scrollLeft = document.documentElement.scrollLeft;
    }

    var topOffset = Math.ceil(viewPortHeight / 2 - element.offsetHeight / 2);
    var leftOffset = Math.ceil(viewPortWidth / 2 - element.offsetWidth / 2);

    var top = scrollTop + topOffset;
    var left = scrollLeft + leftOffset;

    element.style.top = top + "px";
    element.style.left = left + "px";
};