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;