Error: Invalid controller specified (a)

#0 /var/www/html/cliniser.com/web/library/Zend/Controller/Front.php(954): Zend_Controller_Dispatcher_Standard->dispatch(Object(Zend_Controller_Request_Http), Object(Zend_Controller_Response_Http))
#1 /var/www/html/cliniser.com/web/application/Bootstrap.php(138): Zend_Controller_Front->dispatch()
#2 /var/www/html/cliniser.com/web/library/Zend/Application.php(366): Bootstrap->run()
#3 /var/www/html/cliniser.com/web/public/index.php(28): Zend_Application->run()
#4 {main}