function setDivDisplay(aDivName, aDisplay) {
  var d = document.getElementById(aDivName);
  if (d != undefined && d != null)
    d.style.display = aDisplay ? 'block' : 'none';
}

function getDivDisplay(aDivName) {
  var d = document.getElementById(aDivName);
  if (d != undefined && d != null)
    return d.style.display != 'none'
  else
    return null;
}

function toggleDivDisplay(aDivName) {
  var d = document.getElementById(aDivName);
  if (d != undefined && d != null)
    d.style.display = (d.style.display == 'none' ? 'block' : 'none');
}