var boodschap = "Op deze sites geldt het copyright, meer info via MZPC@hotmail.com";

function stelen(keyp) {
  if (navigator.appName == "Netscape" && keyp.which == 3) {
    alert(boodschap);
    return false;
  }
  if (navigator.appVersion.indexOf("MSIE") != -1 && event.button == 2)  {
    alert(boodschap);
    return false;
  }
}
document.onmousedown = stelen