function externalLinks()
{
if (!document.getElementsByTagName) return; 

var anchors = document.getElementsByTagName("a"); 
for (var i=0; i<anchors.length; i++) { 
var anchor = anchors[i]; 
var relvalue = anchor.getAttribute("rel");

if (anchor.getAttribute("href")) {
var external = /external/;
var relvalue = anchor.getAttribute("rel");
if (external.test(relvalue)) { anchor.target = "_blank"; }
} 
}
} 
window.onload = externalLinks;