var validClick = false;

function captureClick(e) {
  var message = "Oops!  This image is copyrighted.";
  validClick = false;
  
  targType = '';
  if (e.target) targType = e.target.tagName;
  else if (e.srcElement) targType = e.srcElement.tagName;
  if (targType != 'IMG') return validClick = true;

  if (document.layers) b = e.which;
  else b = e.button;
  
  if (b > 1) {
    validClick = false;
    alert(message);
    return false;
  }
}

if (document.layers) window.captureEvents(Event.MOUSEDOWN);
document.oncontextmenu = new Function("return validClick;");