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;