var movedownvar = setTimeout('',1);

function move_down(div_scroll,speed)
{
stop = document.getElementById(div_scroll).scrollHeight - document.getElementById(div_scroll).clientHeight ;
//alert(document.getElementById(div_scroll).scrollTop);

if(stop > document.getElementById(div_scroll).scrollTop){
    document.getElementById(div_scroll).scrollTop += speed
    movedownvar = setTimeout("move_down('"+div_scroll+"',"+speed+")",100);
}else{
    document.getElementById(div_scroll).scrollTop = 0;
    movedownvar = setTimeout("move_down('"+div_scroll+"',"+speed+")",100);
}
}

function stop(div_scroll,speed)
{
	prova = clearTimeout(movedownvar);
}