Your Yii web application is configured to run in the development mode environment. The YII_ENV constant (from the Yii entry script) specifies which environment the application is running in. When running in production it's recommended to use the production environment.
To disable dev mode remove the following lines from the Yii entry script
// remove the following line when in production mode defined('YII_ENV') or define('YII_ENV', 'dev');