Page not found (error 404)

The page http://ippolitoborgo.altervista.org/new/wp-admin/admin-ajax.php?action=efbl_generate_popup_html&rand_id=4 was not found on this server.

This can be due to:

Pay attetion to UPPER and LOWER cases
http://site.altervista.org/Page.html is different from http://site.altervista.org/page.html