WordPress Register Style Called Incorrectly

Question

Why am I getting this error?

Notice: wp_register_style was called incorrectly. Scripts and styles should not be registered or enqueued until the wp_enqueue_scripts, admin_enqueue_scripts, or login_enqueue_scripts hooks. Please see Debugging in WordPress for more information. (This message was added in version 3.3.) in /var/www/domain.com/wp-includes/functions.php on line 3792

The code I'm using to include my custom CSS and JS files is:

// Register a custom style and script.
wp_register_style( 'custom_css', get_stylesheet_directory_uri() . '/custom.css' );
wp_register_script( 'custom_js', get_stylesheet_directory_uri() . '/custom.js', array('jquery') );

// Enqueue a custom style and script in pages and posts.
function add_custom_scripts() {
    wp_enqueue_style( 'custom_css' );
    wp_enqueue_script( 'custom_js' );
}
add_action( 'wp_enqueue_scripts', 'add_custom_scripts', 9999 );

Edit: Per Pieter's answer, I changed my code to this and it fixed the problem:

function add_custom_scripts() {
    // Start "Add Custom Scripts."
    wp_register_style( 'custom_css', get_stylesheet_directory_uri() . '/custom.css' );
    wp_register_script( 'custom_js', get_stylesheet_directory_uri() . '/custom.js', array('jquery') );

    wp_enqueue_style( 'custom_css' );
    wp_enqueue_script( 'custom_js' );
}
add_action( 'wp_enqueue_scripts', 'add_custom_scripts', 9999 );

function add_custom_scripts_login() {
    // Start "Add Custom Scripts."
    wp_register_style( 'custom_css', get_stylesheet_directory_uri() . '/custom.css' );
    wp_register_script( 'custom_js', get_stylesheet_directory_uri() . '/custom.js', array('jquery') );

    wp_enqueue_style( 'custom_css' );
    wp_enqueue_script( 'custom_js' );
}
add_action( 'login_enqueue_scripts', 'add_custom_scripts_login', 9999 );

Answer 1

The notice is quite obvious. It is telling you that you are not running wp_register_style() within the wp_enqueue_scripts hook.

SOLUTION

Move your wp_register_script() and wp_register_style() calls to inside your function which is hooked to wp_enqueue_scripts