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;