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(){ return openPopup(this.href); }
      }
   }
}

function openPopup(address){
   var newWindow = window.open(address,'external');
   if(window.focus) newWindow.focus();
   return false;
}

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