1. Registered User presses the “Login” button in the navbar or the “Already have an account” button in the registration page.
2. Registered User fills in the form with his username and his password.
3. Form data is validated.
4. Registered User is logged in and redirected to his news feed.

3.
    a.  Username is not registered or password is incorrect.
        1. Registered User is notified of the error and asked to re-enter his information; Use case continues at step 3.
    b.  Account has not yet been activated through the activation link.
        1. User is asked to check his email for the activation link and given the option to resend the activation email.
    c.  User’s account has been banned.
        1. User is notified that his account has been banned.