I have noticed Hotmail etc. have small graphics with random letters to defeat automated web crawlers from signing up for things.

Similarly, can't having a graphics pic with some text on it and a box to type in the stuff prevent robots from scouring your website folders and pages, stealing all your pictures and jamming your bandwidth?

I would like to have something like that for both general areas and 'over 18' areas.

The over 18 area idea: I have also seen where you have to use a pulldown to enter a valid Birthdate to enter an 'over 18' area or site. How can I get some code or guidelines on what is legal/necessary and how to do it?

I'd really like that kind of thing, where only real users can enter and browse your site.