// JavaScript Document
function scrollImg(){  
    var posX,posY;  
    if (window.innerHeight) {  
        posX = window.pageXOffset;  
        posY = window.pageYOffset;  
    }  
    else if (document.documentElement && document.documentElement.scrollTop) {  
        posX = document.documentElement.scrollLeft;  
        posY = document.documentElement.scrollTop;  
    }  
    else if (document.body) {  
        posX = document.body.scrollLeft;  
        posY = document.body.scrollTop;  
    }  

    var ad=document.getElementById("ad");  
    ad.style.top=(posY+100)+"px";  
    ad.style.left=(posX+50)+"px";  
    setTimeout("scrollImg()",100);  
}