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") == "blank") {
            anchor.target = "_blank";
          }
        }
   }
      window.onload = externalLinks;