function ExternalLinks() {
  if (!document.getElementsByTagName) return;
  var anchors = document.getElementsByTagName("a");
  for (var i=0;i<anchors.length;i++) {
    var anchor = anchors[i];
    if (anchor.getAttribute("href")&&anchor.getAttribute("rel") == "external") anchor.target = "_blank";
  }
}
window.onload = ExternalLinks