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";
        }
 }
}