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;