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;