// script from sitepoint.com
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;