Site won't load properly when opened with .com subdomain

Hello everybody,

My website won't load properly on mobile devices if opened via the subdomain url (www.steefano.com). With properly I mean that there is a resized version with some text and incomplete images or tables messed up and so on.

I.e.
https://drive.google.com/open?id=0B9...193&authuser=0
https://drive.google.com/open?id=0B9...0w4&authuser=0
https://drive.google.com/open?id=0B9...0w4&authuser=0

While, instead, if I use the original url (steefano.altervista.org), it will load properly(ish, showing the above thing for a second but resizing just afterwards).
On pc and macs works normally.

What is going on? Someone could help me?

Thank you!