function externalLinks() {

if (!document.getElementsByTagName) return;

var anchors = document.getElementsByTagName("a");
for (var i=0; i<anchors.length; i++) {
var anchor = anchors[i];
var relvalue = anchor.getAttribute("rel");

if (anchor.getAttribute("href")) {
var external = /external/;
var relvalue = anchor.getAttribute("rel");
if (external.test(relvalue)) { anchor.target = "_blank"; }
}
}
}
window.onload = externalLinks;