CHICAGO - Herbal remedies are often marketed on the Internet with misleading or unproven health claims that violate federal law, according to a study of 443 Web sites to be published in today's Journal of the American Medical Association. Of the 443 Web sites examined by the team from Boston's Brigham and Women's Hospital, 292 claimed their products could cure, prevent or treat a disease. Federal law bars sellers from making health claims not yet approved by the Food and Drug administration. More than half of those 292 sites, or 153, omitted a federally required disclaimer saying the claims had not been evaluated by the FDA and that the products are not intended to treat or prevent disease. And many sites omitted FDA advisories about health problems linked to an herb.