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";  
 }  
}

/* addLoadEvent function by http://simonwillison.net/ */
function addLoadEvent(func) { 
	  var oldonload = window.onload; 
	  if (typeof window.onload != 'function') { 
	    window.onload = func; 
	  } else { 
	    window.onload = function() { 
	      if (oldonload) { 
	        oldonload(); 
	      } 
	      func(); 
	    } 
	  } 
	} 
	 
addLoadEvent(externalLinks);