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"; 
     anchor.title = "This link opens in a new window"; 
   }
 } 
} 

window.onload = externalLinks;