Fail to prepare and prepare to fail. A good website relies on good planning. Usability is no exception.
Requirements Engineering is the process used to capture and document usability requirements and manage them throughout the website's development. It is essentially a project management exercise that:
Requirements Engineering is very good at highlighting user concerns and prioritising key actions. It results in a more focused development process and better resource planning. All in all, it provides a solid basis for a highly usable and accessible website.