function arrondi_act (act){
		var noeud_cible = document.getElementById("menu_h_arrondi");
		if (act == 'survol')
		{
			if (!noeud_cible.hasChildNodes())
			{
				var new_img = document.createElement('img');
				new_img.src ='images/menu_h_arrondi_lt_survol.png';
				new_img.id ='image_arrondi';
				noeud_cible.appendChild (new_img);
			}
		}
		else
		{
			if (noeud_cible.hasChildNodes())
			{
				var old_img = document.getElementById("image_arrondi");
				noeud_cible.removeChild (old_img);
			}
		}
	}