A consortium of Internet majors have launched a global rating system enabling parents to shield their children from sexually explicit and violent material on the Internet. The PICS Platform for Internet Content Selection, has been in the works for nearly a year, and will take several more months to become a useful tool for parents and educators, its primary targets. Under the system, 39 Internet-related firms including America Online Inc, Compuserve Inc, Microsoft Corp, Prodigy Services Co and Netscape Communications Corp will give users software enabling them to block access to material they judge objectionable on the World Wide Web. Parents and teachers will be able to filter out pages according to their own choice of level of violence, sex, nudity and language. Providers will be urged to rate their pages by filling out an electronic questionnaire resulting in a grade for each site. Netscape plans to begin offering a new version of its Navigator browser incorporating the ratings capability by the end of the year.