window.setInterval("doIt()",10);
function doIt()
{
div = document.getElementById("moveImgContainer");
if(document.all){
	currentPos= document.body.scrollTop;
	px="";
}else{
	currentPos = window.pageYOffset;
	px="px";
}
 if(currentPos<=240){
 	currentPos = 240;
 }else{
 	currentPos = currentPos+70;
 }
 
 div.style.top = currentPos+px;
}