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";
     anchor.className += "external-link";
    }
  }   
}   
window.onload = externalLinks;