function change() {

select = document.getElementById("niveau_select");
select_s = select.style;

switch(select.selectedIndex) {

case 0 :
select_s.background = "url('image/element_site/icones/icones/rien.png') no-repeat";
break;

case 1 :
select_s.background = "url('image/element_site/icones/icones/niveau_1.png') no-repeat";
break;

case 2 :
select_s.background = "url('image/element_site/icones/icones/niveau_2.png') no-repeat";
break;

case 3 :
select_s.background = "url('image/element_site/icones/icones/niveau_3.png') no-repeat";
break;

default:
select_s.background = "none";
break;
}
}