by Gareth J Barnard.
Dear Elisa,
Looking at http://utente.altervista.org/moodle/ it says 'Warning: if you have just activated your site you might have to wait up to 24 hours before it is visible.' which might be the issue.
Have you followed http://docs.moodle.org/24/en/Installing_Moodle ?
Looking at http://en.altervista.org/create-free-site.html there are a few supported CMS's have you contacted support to see if Moodle is supported. I know my provider will run Wordpress and Drupal but Moodle will not work because of versions of PHP etc. Only found out after contacting them.
Cheers,
Gareth