Unable to use the categories to block traffic (I'm doing something wrong...)

I'm testing the feature to block some categories and starting out with Computerrelated as an example. I can see that the Ruleset's counters are passing the packets through, but I can't get why it's not blocked. How to test? I'm trying to browse to Tomshardware.com and Anandtech.com but that works - i e - is not blocked :-( I'm applying this to the eth3 where my wifi subnet is and on direction "out", and since the counters works, I guess that implementation is correct. I've also played with the rule itself to set source and destinations, both IP-ranges and interfaces.

    name Wifi_Blocked_Sites {
        default-action accept
        description ""
        rule 1 {
            action drop
            application {
                category TopSites-Computers
            }
            description BlockComputerrelated
            log disable
            protocol all
            source {
                group {
                }
            }
        }
    }

 Edit: Now I can see, the rule is blocking a few packets here and there, but I can still visit some major hardware sites :-/