step = 1;
timer = "";

function scroll(id)
{
	var e = document.getElementById(id);

	clearTimeout(timer);
	e.scrollTop += step;
  
	timer = setTimeout("scroll('"+id+"')", 50);
  
	if (e.scrollTop + e.clientHeight >= e.scrollHeight)
	{
		e.scrollTop = 0;
	}
}

function stop()
{
	clearTimeout(timer);
}