var supported = ((document.getElementById || document.all) && navigator.userAgent.indexOf('Opera') == -1);

var klaar = false;
var onthoud = "";
var pos;

function blocking(i)
{
  if (!supported)
  {
    alert('This link does not work in your browser.');
    return;
  }
  shown[i] = (shown[i]) ? false : true;
  current = (shown[i]) ? 'block' : 'none';
  if (document.getElementById)
  {
    document.getElementById('number'+i).style.display = current;
  }
  else if (document.all)
  {
    document.all['number'+i].style.display = current;
  }
}