Anyone know what this error means?

I had two different websites (let’s call them site A & site B) running WordPress and therefore two different databases. I didn’t need WordPress on site A so I deleted its database. The problem is that site B is now displaying a ‘0’ on every page.

I know I didn’t delete the wrong database because I can still read all the latest comments, posts, etc. inside site B’s database. Does anyone know what it means when a WordPress install just displays a ‘0’?