function afficherCacher(idbouton,idbloc) {
    if (! document.getElementById) return null;
    bouton = document.getElementById(idbouton);
    bloc = document.getElementById(idbloc);
    if (bouton.value == "+") {
	bouton.value = "-";
 	bloc.style.display = "block";
    } else {
	bouton.value = "+";
	bloc.style.display = "none";
    }
}
function swapAfficherCacher(id1,id2) {
    if (! document.getElementById) return null;
    b1 = document.getElementById(id1);
    b2 = document.getElementById(id2);
    b1.style.display = "none";
    b2.style.display = "block";
}