function showRappel()
{
	i = document.getElementById('rappel');
	ww = document.body.clientWidth;
	wh = document.body.clientHeight;
	iw = parseInt(i.style.width);
	ih = parseInt(i.style.height);
	l = (ww-iw)/2;
	t = (wh-ih)/2;
	i.style.left = l+"px";
	i.style.top = t+"px";
	i.style.display = (i.style.display == "none" ? "" : "none");
}