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;