RSS bookmarks in Safari do not update their unread news number

"Thanks to Benjamin, I've found what it is. Safari preferences only proposes to update RSS feeds located in your Bookmarks bar or in the Bookmarks menu (depending on what options you check in).

Actually some of my bookmarks where located in special directory you can create when clicking on the Bookmark link (the button is located in the left of the bookmark bar right below the previous/next web page button, you know, it represents an open book).

I've copied all my RSS feeds in the Bookmark menu, and now everyone get updated."