function addLoadListener(fn) {
  if (typeof window.addEventListener != 'undefined') {
    window.addEventListener('load', fn, false);
  } else if (typeof document.addEventListener != 'undefined') {
    document.addEventListener('load', fn, false);
  } else if (typeof window.attachEvent != 'undefined') {
    window.attachEvent('onload', fn);
  } else {
    var oldfn = window.onload;
    if (typeof window.onload != 'function') {
      window.onload = fn;
    } else {
      window.onload = function() {
        oldfn();
        fn();
      };
    }
  }
}

function externalLinks() {
	x = document.getElementsByTagName('a');
	if(!x) return false;
	for (var i = 0; i < x.length; i++) {
		if (x[i].getAttribute("href") && x[i].getAttribute("rel") == "external") {
			x[i].target = '_blank';
		}				  
	}
}
addLoadListener(externalLinks);