function setTargetsForExternalLinks() {
  if (!window.document.getElementsByTagName) {
    return;
  }
  var listOfAnchorElements = window.document.getElementsByTagName("a");
  var regExp = new RegExp("\\b" + "external" + "\\b");
  for (var i=0; i<listOfAnchorElements.length; i+=1) {
    var anchor = listOfAnchorElements[i];
    if (anchor.getAttribute("href") && (anchor.getAttribute("rel")) && (anchor.getAttribute("rel").search(regExp) != -1)) {
      anchor.target = "_blank";
    }
  }
};
window.onload = setTargetsForExternalLinks;