function externallinks() {
   anchors = document.getElementsByTagName("a");
   for (var i=0; i<anchors.length; i++) {
     rel = anchors[i].getAttribute("rel");
     if (rel == "external") {
        target = document.createAttribute("target");
        target.nodeValue="_blank";
        anchors[i].setAttributeNode(target);
     }
   }
}