function externalLink() {
   if (document.getElementsByTagName) {
      var links = document.getElementsByTagName('a');
      for (var i = 0; i < links.length; i++) {
         var link = links[i];
         if (link.getAttribute('href') && link.getAttribute('rel') == 'blank') {
            link.target = '_blank';
	     }
      }
   }
}

if (window.onload != null) {
   var onload = window.onload;
   window.onload = function() { 
      onload(); externalLink(); 
   };
} else {
   window.onload = externalLink;
}