Chances are this is the actual permalink for the post:
http://alessandrognola.com/ecommerce-limportanza-della-comunicazione-con-il-cliente/
This URL:
http://alessandrognola.com/ecommerce-comunicazione-cliente/
Gets rewritten by the web server and redirects clients to http://alessandrognola.com/ecommerce-limportanza-della-comunicazione-con-il-cliente/
There is actually no page here http://alessandrognola.com/ecommerce-comunicazione-cliente/
[~/]$ curl -I 'alessandrognola.com/ecommerce-comunicazione-cliente/'
HTTP/1.1 301 Moved Permanently
Date: Mon, 17 Nov 2014 15:06:40 GMT
Server: Apache
X-Pingback: http://alessandrognola.com/xmlrpc.php
Expires: Wed, 11 Jan 1984 05:00:00 GMT
Cache-Control: no-cache, must-revalidate, max-age=0
Pragma: no-cache
Location: http://alessandrognola.com/ecommerce-limportanza-della-comunicazione-con-il-cliente/
Content-Type: text/html; charset=UTF-8
There is nothing to worry about. The content exists at just one location, and the webserver is directing the incorrect access to the proper URL.
Chances are you saved that post with the old permalink and then changed the post title and maybe the permalink. If you go to edit the post, edit the permalink, remove the permalink that is there and then click OK to let WordPress create the permalink, then you will have just one post with one permalink.
This assumes you did not do anything crazy in your .htaccess file to actually redirect one URL to another.
For example, this does not exist either, correct?
http://alessandrognola.com/ecommerce-limportanza-della
However, if you enter that in the browser, it will redirect to http://alessandrognola.com/ecommerce-limportanza-della-comunicazione-con-il-cliente/ as well.
There is an Apache module called mod_speling which is probably trying to be helpful by guessing what you really meant.
