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;

// New HTML5-friendly function

$(function() {
    $('a.new-window').click(function() {
        window.open(this.href);
        return false;
    });
});