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;