function newwindowLinks() {
 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") == "newwindow") 
       anchor.target = "_blank"; 
 }
} 
window.onload = newwindowLinks;