var cury = 0;

function getObject(name) {
   var ns4 = (document.layers) ? true : false;
   var w3c = (document.getElementById) ? true : false;
   var ie4 = (document.all) ? true : false;

   if (ns4) return eval('document.' + name);
   if (w3c) return document.getElementById(name);
   if (ie4) return eval('document.all.' + name);
   return false;
}


function updatePosition() {
  var desty = document.body.scrollTop + 6;

  if( cury != desty ) {
    if( desty - cury > 100) { cury = desty - 90; }
    if( cury - desty > 100) { cury = desty + 90; }
    var newy = Math.round( cury + ((desty - cury) / 5) );
    getObject("fg_media_stalker").style.top = newy;
    cury = newy;
  }
}

window.onload = function() {
  setInterval(updatePosition, 20);
}