Applying Web usability criteria for vision-impaired users: does it really improve user task performance?

Available accessibility guidelines do not necessarily guarantee usable web sites, in particular when specific groups of disabled users are considered. We have identified 15 Web design criteria aiming to provide integrated support of accessibility and usability for vision-impaired users. In this paper, we present the results of a study investigating whether the application of such guidelines for vision-impaired users can actually improve their task performance when accessing Web applications. We report on two user tests, both involving vision-impaired users, which aim to provide empirical validation of the design criteria. During each test, users had to access and navigate two versions of a Web site: one version supporting the selected design criteria and one obtained with traditional techniques. Our results indicate that the 15 design criteria improved Web site usability both quantitatively and qualitatively by reducing the navigation time needed to perform the assigned tasks and by making the Web sites easier to navigate for blind and low-vision users.