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") != null) && anchor.getAttribute("rel").indexOf("external") >=0 )   
		anchor.target = "_blank";   
	}   
 }   

window.onload = externalLinks;