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"))
      {
         var rel = anchor.getAttribute("rel");
         if (rel.substr(0,8) == "external")
            anchor.target = "_blank";
      }
   }
}

window.onload = function(){
   externalLinks();
}