function enablePopups(){
   if(!document.getElementsByTagName) return;
   var linkElements = document.getElementsByTagName("A");
   for(var i = 0; i < linkElements.length; i++){
      var r = linkElements[i].rel;
      if(r.indexOf("external")!=-1){
         linkElements[i].onclick = function(){
            var newWindow = window.open(this.href,'external');
            if(window.focus) newWindow.focus();
            return false;
         }
      }
   }
}

window.onload = function(){
   enablePopups();
}