var pic = new Array();
pic[0]=new Image();
pic[0].src="ressources/images/star0.png";
pic[1]=new Image();
pic[1].src="ressources/images/star.png";
 
function rate(level){
  for(i=1;i<6;i++){
    document.getElementById('_'+i).src=(level<i)?pic[0].src:pic[1].src;
  }
}