The National Association of the Deaf on Thursday sued Harvard University and the Massachusetts Institute of Technology, saying the institutions violate the Americans with Disabilities Act of 1990 and the Rehabilitation Act of 1973 by not captioning all of the course content they make available online. Some of the content, NAD said, relies on automatic captions provided by Web sites such as YouTube, which sometimes produce unintelligible captions depending on audio clarity, while other videos don't offer captions at all. The cases are filed in a federal district court in Massachusetts.