Legal requirements for accessibility
It is almost certainly a legal requirement that web sites be usable by users with disabilities. In a university environment, the Special Educational Needs and Disability Act (2001) is of particular importance, and provides students (and applicants) with disabilities with legal protection from discrimination. Other parts of the Disability Discrimination Act (1995) provide similar legal protection to employees of the university and people that the University provides services to - for example conference guests or business partners.
There is a requirement for reasonable adjustments to be made to ensure that no-one is treated less favourably than someone else for a reason related to his or her disability without justification.
This requirement is unfortunately vague, and there is currently no British case law on the matter. Therefore, until a test case is heard by the courts, the exact applicability of the law to web design remains unknown.
The Journal of Information, Law and Technology has an article on legislation and the web, giving the opinion that "...the accessibility of Web sites provided by service providers does fall within Part III of the DDA...".