I am trying to en-queue css in worpress. Here is my code

    function amba_adding_styles()
{
    wp_register_script( 'jquery-ui-css', 'http://code.jquery.com/ui/1.10.3/themes/smoothness/jquery-ui.css');
    // Register the style like this for a plugin:
    wp_register_style( 'custom-style', plugins_url( '/css/custom-style.css', __FILE__ ), array(), '20120208', 'all' );

    // For either a plugin or a theme, you can then enqueue the style:
    wp_enqueue_style( 'jquery-ui-css' );
    // For either a plugin or a theme, you can then enqueue the style:
    wp_enqueue_style( 'custom-style' );
}
add_action( 'wp_enqueue_scripts', 'amba_adding_styles' );

However, jquer-ui.css doesnt load. Can anybody guess the error here??