The two terms 'usability' and 'accessibility' are frequently used when talking about website design, often interchangeably, without ever defining what is meant.
Accessibility is a general term used to describe the degree to which a system is usable by as many people as possible. More specifically for web, accessibility means that people with disabilities can perceive, understand, navigate, and interact with the web.
The UK Disability Discrimination Act (DDA) 1995 has numerous provisions for accessibility, none of which refers explicitly to websites, but make it illegal to discriminate against people with disabilities.
How does that apply to my website?
The good news is that the overall accessibility of the website is largely embedded in the CMS and is looked after by CiCS. They try to make the website adheres to accessibility rules as defined by W3C Web Accessibility Initiative (WAI), although this has been modified in accordance with advice from RNIB.
There are however specific considerations and rules that should be adhered to when designing the content of a website.