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;