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;