function update_online ()
{
    $.ajax({
      url: '/online_users',
      type: 'POST',
      dataType: 'html',
      success: function(data, textStatus, xhr) {
          /* $( '#currently_online' ).html( data ); */
          if ( data != $( '#currently_online' ).html() )
          {
              $( '#currently_online' ).fadeOut( 'normal', function(){
                 $( this ).html( data );
                 $( this ).fadeIn( 'fast' ); 
              });
              setTimeout( update_online, 3000 );
          }
          else
          {
              setTimeout( update_online, 3000 );
          }
      }
    });
};

$(document).ready(function() {
    setTimeout( update_online, 3000 );
});