The main idea of web accessibility is how to design and develop websites to benefit all web users. The ultimate purpose of web accessibility is to develop barrier-free environment on the Internet. However, most websites have overlooked the problem of the web accessibility. This paper introduces the significance of web accessibility and the related web accessibility guidelines, provides general design principles for web accessibility and the development techniques of the accessible web pages. It contributes to increase the accessibility of websites and better develop barrier-free websites.