function externalLinks() {
    if (!document.getElementsByTagName) return;
    var anchors = document.getElementsByTagName("a");
    for (var i=0; i<anchors.length; i++) {
        var anchor = anchors[i];
        var relBlank = anchor.getAttribute("rel");   
        var relArray = new Array(); 
        if(relBlank != null)  
          relArray = relBlank.split(' '); 
        if (anchor.getAttribute("href") && relArray.indexOf("blank") >= 0)
            anchor.target = "_blank";
    }
}
window.onload = externalLinks;