A: 

With google WebMaster Tools you can test your robots.txt.

http://www.google.com/webmasters/

Arthur
this isn't my website
xRobot
A: 

Have you disallowed all bots, or is this rule just for the Googlebot? If it's the latter, you need to ensure that you also include the rule for the 'Googlebot-Image' user agent.

Dave R.
this is not my website :(
xRobot
+1  A: 

Because of the different domain names (actually a domain and a subdomain): the page is from http://www.alvolante.it and the image is from http://immagini.alvolante.it.

Robots.txt is only in the www domain. If the file would be also in http://immagini.alvolante.it/ the Google wouldn't indexed the image.

Try to access http://immagini.alvolante.it/sites and http://www.alvolante.it/sites and you will see different pages.

Parkyprg
but robots.txt is also in the subdomain: http://immagini.alvolante.it/robots.txt
xRobot