The World Wide Web Consortium (W3C) has the best recognised 'Content Accessibility Guidelines', and they ask sites to be 'Double A minimum' and 'Triple A' preferred. To see what this means, visit http://www.w3.org/
TechDis is a Joint Information Systems Committee funded service supporting the further and higher education community in all aspects of technology and disabilities and/or learning difficulties.
This site is comprehensive, clear and accessible (as you'd hope it would be given the title !). There are various tools, resources and materials, and it is possible to evaluate web sites for accessibility, look at your curriculum in terms of accesibility, and keep in touch with news in this important area. http://www.techdis.ac.uk
Web site design etc. "What Makes a Great Web Site?" by WebReference.com http://www.webreference.com/greatsite.html
"What are the essential traits of great Web sites? After you visit a
site and find yourself staying awhile, what makes you stay? A sense of
humour helps. Flashy graphics are nice. But the fundamental traits that
make a site work are more elusive. This article will break down the
essential characteristics of great Web sites into some easily followed
rules of thumb."