var contenu = null;
var recipient = null;
var tdmiddle = null;
var tdwidth = 0;
var h_cont, h_recip, timer, pas, pos = 0;

function init() {
   contenu = $('contenu');
   recipient = $('recipient');
   h_cont = contenu.offsetHeight;
   h_recip = recipient.offsetHeight;
   timer = 0;
   pas = 1;
   move();
}

function move() { 
   if (timer == 0) {	
      timer = setInterval("roll()", 30) 
   }
} 

function roll() {
   if (pos < - h_cont) {
      pos = h_recip;
   } else {
      pos -= pas;
   }
   contenu.style.top = pos + 'px';
}

function stop() { 
	if (timer != 0) {
		clearInterval(timer)
		timer = 0
	}
}