Applying Web Usability Criteria for Vision-Impaired Users: Does It Really Improve Task Performance?

However, accessibility alone is not enough. Usability aspects need to be addressed as well. Indeed, accessibility and usability are frequently addressed
as two separate issues, but disabled users need to have both accessible and usable applications. In fact, accessibility and usability are two intertwined
aspects of Web site interaction, and if they are not properly integrated, Web sites can turn out to be either accessible but barely usable or usable but
barely accessible. In both cases Web site navigation by disabled users is likely to be seriously compromised, because they either may not be able to access the desired information (i.e., it is not accessible) or may find difficulty in arriving at what they need (in this case it is not usable).