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;