54% of parents with teens who have access to the Internet have filtering software installed on home computers, up from 41% in 2000, the Pew Internet and American Life Project study found. 13% of American teens do not use the Internet at all. 62% of parents of online teens say they check the sites their children visit, though only a third of teens who use the Internet at home believe their parents do so. And any reasonably tech-savvy teen knows how to erase their online footsteps.