I have downloaded the worpress from online. The following code is in config.php.
define('AUTH_KEY', 'put your unique phrase here');
define('SECURE_AUTH_KEY', 'put your unique phrase here');
define('LOGGED_IN_KEY', 'put your unique phrase here');
define('NONCE_KEY', 'put your unique phrase here');
define('AUTH_SALT', 'put your unique phrase here');
define('SECURE_AUTH_SALT', 'put your unique phrase here');
define('LOGGED_IN_SALT', 'put your unique phrase here');
define('NONCE_SALT', 'put your unique phrase here');
Even if i don’t define any key my site runs fine. Is it compulsory to define those keys? If i don’t define them are they affect my site? Please explain.
In the following location you can find the detailed explanation of your question. I hope this helps. Thanks
http://codex.wordpress.org/Editing_wp-config.php#Security_Keys