How to block access to specific web sites

I’m using CPF latest version
I have added specific websites to “My Blocked Network Zones” in the form
However, the sites are not being blocked.
Am I missing something (again)??
Thanks in advance for your input.

use an ip address, not the name. So for yahoo, block and you will see it works. In windows if you want to find the ip address just open the cmd and put this in tracert and the last ip listed will be that websites ip address.