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