At the Boston Public Library, president Bernard Margolis explains, the children's and teenagers' rooms have Internet terminals that filter out porn. The grown-ups use different computers and can visit the Flesh Public Library or order the Flesh Gordon video. If a person under 18 wants access to the wider world of Web wonders, he or she can get it, with signed permission from a parent. ''That puts the decision with the parent, where it belongs, and not with us,'' Margolis says.