$(document).ready(function() {
  externalLinks(); 
});

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";   
 			   
		}
}