function ext_link() {
	if (!document.getElementsByTagName) return;
	var el = document.getElementsByTagName("a");
	for (var i=0; i<el.length; i++) {
		var l = el[i];
		if (l.getAttribute("href") &&
				l.getAttribute("rel") == "ext")
				l.target = "_blank";
	}
}
addOnloadEvent(ext_link);