The Web has become one of the most important communication media, since it is spread all over the world. In order to enable everyone to access this medium, Web accessibility has become an emerging topic, and many techniques have been evolved to support the development of accessible Web content. This paper presents a survey on techniques for Web accessibility and proposes a classification into the processes of ISO/IEC 12207 standard. The survey was carried out applying systematic review principles during the literature review. The results include analysis obtained from the synthesis of 53 studies, selected from an initial set of 844. Although the survey results indicate a growth in research on techniques for design and evaluation of Web applications, they also indicate that several development activities have been poorly addressed by scientific research efforts.