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;