Criteria to improve web site usability and accessibility when interacting through screen readers: definition, application, and evaluation

This research is related to the usability and accessibility of Web sites. Guidelines for Web site usability already exist, but they only marginally consider the exigencies of "special users", such as blind people or subjects with high levels of vision deficit. This study specifically aimed at defining, in a more precise way, the usability of Web sites, in order to improve their accessibility for "special users", who are obliged to navigate on the internet through screen readers. First of all, 19 criteria (general principles) and 54 checkpoints defining each criterion (technical solutions) were proposed; then, possible ways of application of such criteria and checkpoints was specified. This represented the starting point to evaluate the usability of Web sites: in this work, the heuristic-based method was proposed and used in order to assign levels of usability to several Web sites of interest. A user testing was performed by 15 voluntary users, chosen among blind and low vision subjects. Two Web site prototypes were specifically designed for this purpose, only differing for the presence/absence of important usability criteria defined in this study. By comparing the time spent by users navigating and performing assigned tasks on the two Web site (with and without criteria), the impact of the application of the proposed criteria on the quality of the navigation was estimated. Finally, an automatic tool, whose implementation is in progress, is briefly presented at the end of this work. This tool is the first step toward a complete and definitive automatic procedure able to evaluate real Web site usability, especially considering blind and low vision people's constraints. Further studies are in progress to reach this final goal.