The objective of this study is to investigate the current accessibility initiatives applied to the Web and identify its main characteristics and trends. The method used was a literature review focused on work in the last twenty years in the United States, United Kingdom, Australia, Canada and Brazil, ranked according to their approaches, in six lines of study. As a result, points out the lack of studies that allow effective analysis of the accessibility of websites, and methods for continuous improvement of technical standards and recommendations. It follows, showing the application of usability metrics by Nielsen and ISO-9241 and the incorporation of research models of information behavior seeking for assessment of gaps in accessibility.