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;