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;