lastScrollY = 0;
function heartBeat()
{
    var diffY;
    if (document.documentElement)
        diffY = document.documentElement.scrollTop;
    else if (document.body)
        diffY = document.body.scrollTop;

    percent = .1 * (diffY - lastScrollY);
    if(percent > 0) percent = Math.ceil(percent);
        else percent = Math.floor(percent);
    document.getElementById("loading").style.top = parseInt(getId("loading").style.top)+percent+"px";
    lastScrollY = lastScrollY + percent;
}	
window.setInterval("heartBeat()",1);