The checkout/onepage is working with https. But, why checkout/cart is not?

http://idfr.com/checkout/cart/
https://idfr.com/checkout/onepage/

Here is fragment of the .htaccess:
############################################
## enable rewrites

Options +FollowSymLinks
RewriteEngine on
# RewriteCond %{REQUEST_URI} checkout\/onepage
RewriteCond %{HTTPS} off
RewriteCond %{REQUEST_URI} checkout/
# RewriteRule ^(.*)$ https://%{HTTP_HOST}/$1 [R=301,L]
RewriteRule ^checkout/$ https://idfr.com/checkout/ [R=301,L]

############################################


- Apache version: Apache/2.4.7 (Ubuntu)
- operating system: Windows 8.1
- indications in the log files; Main ErrorLog: "/var/log/apache2/error.log"