Nielsen Norman Group (NNG) is a consulting and research firm, specializing in user experience and usability. NNG conducts research on design trends around the world, across industries, companies, and user types. They have a number of publications that provide simple design guidelines that anyone can follow to improve user experience and usability, including reports on user centered design methodology and reports for special audiences like senior citizens, children, teenagers, college students, and users with disabilities.
The report “Beyond ALT Text: Making the Web Easy to Use for Users With Disabilities” is offered for free on the NNG website.