function external()
 {
   if (document.getElementsByTagName)
    {
     var anchors = document.getElementsByTagName("a");
     for (var i=0; i<anchors.length; i++)
      {
       var anchor = anchors[i];
       if (anchor.getAttribute("rel") == "external")
        {
         anchor.target = "_blank";
        }
      }
    }
 }
window.onload = external;