base_url() and 403 error in CodeIgniter
Change permission of assets/css/style.css to 644
Change base url as follows
$config['base_url'] = 'http://www.jedendzien.pl/';
Or If you have a secure url,Then
$config['base_url'] = 'https://www.jedendzien.pl/';
Change .htaccess to
RewriteEngine OnRewriteCond %{REQUEST_FILENAME} !-fRewriteCond %{REQUEST_FILENAME} !-dRewriteRule ^(.*)$ index.php/$1 [L]
For absolute url you should include protocol, it may be relative like this:
<link href='//www.jedendzien.pl/assets/css/style.css' rel='stylesheet'>
Try this .htacces content:
RewriteEngine onRewriteCond $1 !^(index\.php|assets)RewriteRule ^(.*)$ /index.php/$1 [L]