function update_city_select(){
  var prefecture_id = $('prefecture_id').value;
  var isMSIE = /*@cc_on!@*/false;
  var toReplace = "";
  if( isMSIE ){
    toReplace = "city_div";
  }else{
    toReplace = "city_id";
  }
  new Ajax.Updater(
		   toReplace,
		   "/ajax/cities/" + prefecture_id + "?ie=" + isMSIE,
		   {
		     method: "get",
		     onSuccess: function( request ){
		       document.getElementById('city_city_id').innerHTML = request.responseText;
		     }
		   });
}