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;