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+window.screen.width-150)+"px";
    setTimeout("scrollImg()",100);
}