function startIframe(url) {
  var cDiv = document.getElementById('maincontent');
  cDiv.innerHTML = "";
  var iFrame = document.createElement("IFRAME");
  // iFrame.src = "http://www.dirtyhill.nl/"+url;
  iFrame.src = url;
  iFrame.setAttribute('width','100%');
  iFrame.setAttribute('height','95%');
  iFrame.setAttribute('border','0');
  cDiv.appendChild(iFrame);
}