/* in questo caso definiamo la variabile "prev" nel file html che include lo script */
 var prev= null;

window.onload=function() {
  if (document.getElementsByTagName && document.getElementById) {
    document.getElementById("menu_verticale").className="jsEnabled";
    BuildList();
  }
}

function BuildList(){
    var hs=document.getElementById("menu_verticale").getElementsByTagName("h3");
    for (var i=0; i<hs.length; i++) {
        hs[i].onclick=function() {
            if (this.parentNode.className!="show") {
              this.parentNode.className="show";
              if (prev && prev!=this.parentNode) prev.className="hide";
              prev=this.parentNode;
            } else this.parentNode.className="hide";
        }
    }
}