One proposal I have seen that involves HTML is that any page that contains
adult material would send some kind of identifier to the web browser as it
connects. If the web browser is configured to allow viewing of adult
material (presumably by the parent), access continues. If not, a dialog is
displayed and access is terminated. Not perfect obviously, but a good
start.
The same handshaking could be done between the CU client software and the
reflectors. Any reflector that allows adult material could have a flag set
in its configuration file that would initiate the confirmation with the
connecting client.
I feel that doing something like this pro-actively might save some headaches
down the road, as well as furthering the goal of being 'internet friendly'.
Just one persons opinion.