add one folder any name e.g public and add .htaccess file and write allow from all it means, in this folder your all files and all folder will not give error Access forbidden! use it like this
<link href="<?php echo base_url(); ?>application/public/css/style.css" rel="stylesheet" type="text/css" />
<script type="text/javascript" src="<?php echo base_url(); ?>application/public/js/javascript.js"></script>