What we store about our users:
Nothing!
Yes, it's that simple. We do not store any information about our individual users. When a user visits a website, the address of the website is sent off to our server, but it is not in any way tied to the user. The address of the website is stored in a database, but again, with no relations to the user.
In the future we have plans for making it possible to create a user account on our service, so that the users can help support the project and get access to additional information about the websites they visit. More on this later!