On average, when you ask someone to perform a task on a site, they cannot do it. It's not their fault; it's the designer's fault.
Jakob NielsenDeveloping fewer features allows you to conserve development resources and spend more time refining those features that users really need. Fewer features mean fewer things to confuse users, less risk of user errors, less description and documentation, and therefore simpler Help content. Removing any one feature automatically increases the usability of the remaining ones.
Jakob NielsenUltimately, users visit your website for its content. Everything else is just the backdrop.
Jakob NielsenThe system should speak the users' language, with words, phrases and concepts familiar to the user, rather than system-oriented terms. Follow real-world conventions, making information appear in a natural and logical order.
Jakob NielsenOn the Web, usability is a necessary condition for survival. If a website is difficult to use, people leave. If the homepage fails to clearly state what a company offers and what users can do on the site, people leave. If users get lost on a website, they leave. If a website's information is hard to read or doesn't answer users' key questions, they leave. Note a pattern here?
Jakob Nielsen