4) Additional steps when a desired URL is blocked by the Blacklist:
If a desired URL is blocked by the URL / Content Filter of the Unified Firewall, it must be checked why it is blocked.
4.1) In the Unified Firewall go to the menu Monitoring & Statistics → Settings and for the parameters Web Content Allowed und Web Content Blocked select the option Save Raw Data Locally, so that messages regarding the URL / Content Filter are logged to the Alert Log. Click Save afterwards.