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.className == "external"){
   anchors[i].target = "_blank"
   }
 } 
} 
window.onload = externalLinks;