If you are unable to view the user interface using Microsoft Internet Explorer but you have entered the correct address and it has not allowed access to the interface, check the http:// or https:// part of the URL.
For example:
http://ip_address_of_smoothwall:81
or
https://ip_address_of_smoothwall:81
Also, see our knowledge base article, Regaining Access to the Administration UI After Creating an Access Rule to Block Traffic.