// JavaScript Document
function visibilite(thingId)
{
 var i;
 var targetElement;
 for(i=1; i<4; i++){
  targetElement = document.getElementById("elem" + i) ;
  targetElement.style.display = "none" ;
 }
 targetElement = document.getElementById("elem" + thingId) ;
 targetElement.style.display = "block" ;
}