var lastopen=null;
 
function apri(obj)
 {
 a=document.getElementById(obj);
 a.style.display="block";
 if ((document.getElementById(lastopen))&&(obj!=lastopen))
  {
  chiudi(lastopen);
  }
 lastopen=obj;
 }
 
function chiudi(obj)
 {
 a=document.getElementById(obj);
 a.style.display="none";
 }
 
function toggle(obj)
 {
 a=document.getElementById(obj);
 if (a.style.display=="none") { apri(obj); }
 }