Include the CSS file in CodeIgniter

define('URL','http://localhost/CodeIgniter/');
define('IMG',URL.'assets/img/');
define('CSS',URL.'assets/css/');
define('JS',URL.'assets/js/');

In config.php:

$config['base_url'] = URL;

In view:

<link rel="stylesheet" href="<?php echo(CSS.'bootstrap.min.css'); ?>">