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;