WCAG 2.0 has played an important role on Web accessibility. Evaluation of Web accessibility is carried out to conform to WCAG 2.0. Authors and evaluators consult specific techniques of WCAG 2.0 to achieve Web accessibility. Web accessibility, however, is not techniques issues but a communication problem. W3C/WAI has just started a task force to perform preliminary development of a new version of accessibility guidelines. So, now is a good time to reconsider Web accessibility guidelines which focus on communication problems of users. To have a rationale of requirements for upcoming version of Web accessibility guidelines, the proposed paper tries to draw a holistic view of Web accessibility in terms of communication model, which is derived from semiotics. This model uses triangle relationship, authors (developers), content, and users, of WAI model. Authors have a message they want to present to users. The message is encoded with Web technologies into content. Multi-modal content is decoded by user agents and assistive technologies to send a message as view-ports to users. You must notice that the relation between authors and content is unidirectional. The relation between content and users, however, is bidirectional. Users, who have a goal, interact with content through user agents and assistive technologies in a specific context of use. Based on this model, the following 4 points are discussed: (1) It is possible that users interact with content but it is not possible that users interact with authors, which makes communication difficult. (2) We must pay more attention to users’ goal and context when evaluating Web accessibility. (3) Evaluation guideline which does not focus on WCAG but approach Web accessibility from user side is needed. User-centered evaluation is important. (4) To compensate a lack of communication between authors and users, an intelligent content is needed.