Hi,

I'm try to use k2 with a custom Template but when i try to view the item in front-end i see browser error screen 500.

Enable error reporting and set it to development to see the actual issue.
This setting is located in your site's global configuration menu.

I cannot see debug console. This is my k2 item url: www.fotocolizzi.com/component/k2/item/1-test-item.html
This is page that go to item: www.fotocolizzi.com/album-menu.html

Thanx

This is a template error.
With the default template, the item is functioning properly.www.fotocolizzi.com/component/k2/item/1-test-item.html?template=protostar

You need to address this issue to the template's developer.