Recently it was pointed out that the blog displayed old vacancies under the catgeory tab jobs: http://icardablog.wordpress.com/category/jobs/
WordPress does not offer a feature to simply 'unpublish' posts, however there are many plugins that can achieve that effect.We don't want to simplky delete old posts, but need to archivew them.
The simple and dirty solution is to set posts to 'private', this can even be done via the quick edit menu. This means they will reamin visible to administrators only, but will be hidden from view for most other users.