function switchDiv(n) {
   var id;
   var hide = 0;
   switch(n) {
      case 1 : id = "question1"; break;
      case 2 : id = "question2"; break;
      case 3 : id = "question3"; break;
      case 4 : id = "question4"; break;
      case 5 : id = "question5"; break;
      case 6 : id = "question6"; break;
      }
   if ( document.getElementById(id).style.display == "block" ) hide = 1;
   document.getElementById('question1').style.display = "none";
   document.getElementById('question2').style.display = "none";
   document.getElementById('question3').style.display = "none";
   document.getElementById('question4').style.display = "none";
   document.getElementById('question5').style.display = "none";
   document.getElementById('question6').style.display = "none";
   if ( hide != 1 ) document.getElementById(id).style.display = "block";
   }