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;