I’ve talked in class about PAS 78:2006 (now withdrawn) and the development of BS 8878 as a non-technical document designed to inform web site owners about web accessibility. BS 8878 has now been released.
Overview from Out-law.com – Web accessibility code of practice launched by BSI
More information – BS 8878:2010 Web accessibility. Code of practice
It’s available to students from http://www.library.mmu.ac.uk/eresource/dbb.php then scroll down to British Standards Online and log in.