To be able to change settings throught the GUI, IPCop requires your browser to send referer info. If the browser does not send referer info, modifications are ignored and ’Invalid referer: doesn’t match servername!’ is logged. Referer settings can be found/modified: in FF open about:config, search for network.http.sendRefererHeader and modify from 0 to 1 (or 2 which is default). in Opera go Tools→Preferences→Network and tick ’Enable referrer logging’.