function Layer(sNiveau, sNomId, sImgNameArrow) {
	var el = document.getElementById(sNomId);
	var intIndImgPos = sNomId.length-1;
	var intNoDiv = sNomId.substr(sNomId.indexOf('_') + 1, sNomId.length - sNomId.indexOf('_') + 1);
	var elImg = sImgNameArrow + intNoDiv;
	var sDisplayLayer = el.style.display;
	if (sDisplayLayer == '') {
		sDisplayLayer = 'none';
	}
//alert(sNiveau + ' : ' + sDisplayLayer + ' --> ' + elImg);
	if (sDisplayLayer == 'block') {
		el.style.display = "none";
		document.images[elImg].src = sNiveau + 'images/fleche_on.gif';
		document.images[elImg].title = 'Ouvrir';
	} else if (sDisplayLayer == 'none') {
		el.style.display = "block";
		document.images[elImg].src = sNiveau + 'images/fleche_off.gif';
		document.images[elImg].title = 'Fermer';
	}
}