Web design, first and foremost, is a form of formatting. Much like formatting any document, web design is at its best when the designer knows the audience (or, in this case, "the user") and knows how the user will work with the document. Because an element of web design is interactivity, it is incredibly important to consider the user in terms of navigation and other actions.
This section describes the basics of understanding your users, especially in terms of accessibility. Accessibility is not just limited to people with disabilities. Browser compatibility and software functionality are also important components to accessible web design. Moreover, most people who work in web design make a few faulty assumptions that can severely limit the access some of the users have to the website's materials.