It also means, in Web context, Adult Verification Systems, that's to say, a system that attempts to verify that the person seeing the site is indeed an adult and can be exposed to vast amounts of pornography and senseless violence.

Some AVS systems are reputable, others are little more than scams to fleece the gullible.

What is really sweet is when dumbass webmasters protect with an AVS the index page of their site, but leave the image directories wide open. Sooner or later the URL of those directorioes gets out, typically posted on, and traffic to the site sharply increases as the pr0n is being leeched (in case you are wondering how, it is done very easily with wget).