function addEvent(elm, evType, fn, useCapture) {
  // cross-browser event handling for IE5+, NS6 and Mozilla
  // By Scott Andrew
  if (elm.addEventListener) {
    elm.addEventListener(evType, fn, useCapture);
    return true;
  } else if (elm.attachEvent) {
    var r = elm.attachEvent('on' + evType, fn);
    EventCache.add(elm, evType, fn);
    return r;
  } else {
    elm['on' + evType] = fn;
  }
}

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"; 
 } 
} 

addEvent(window, 'load', externalLinks, false);