// JavaScript Dokument - løsning findes på http://www.webmasterworld.com/forum21/11165.htm
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;