Login after disabling the User login block
If you disabled the User login block and need to login, you can visit the login page on:
http://example.com/?q=userThe alternative http://example.com/user will only work when clean URLs are enabled.
Note: Use the literal word user, not your username or user id.

Logout after disabling the Navigation block
If you can't access the logout link and need to logout, you can do so by visiting:
http://example.com/?q=logoutThe alternative
http://example.com/logoutwill only work when clean URLs are enabled.