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;