Can a website have a box?

I’ve been sent a couple of books to review for O’Reilly, which I’ll get to soon, but I’m intrigued by the text on the front of the book. Both are for websites – Wikipedia and Facebook – and are both part of the Missing Manual series. I’m confused though – both also quote the Missing Manual mantra:

The book that should have been in the box

Can a website have a box?