function doScroll()
{
  scrollPos -= 4;
  if(scrollPos<-2096)
    scrollPos += 2096;
  Element.setStyle('marques-img', {'marginLeft': scrollPos + 'px'});
}
function scrollInit()
{
  window.setInterval('doScroll()', 100);
}
var scrollPos = 0;
Event.observe(window, 'load', scrollInit);