Proposing new metrics to evaluate web usability for the blind

Accessibility-related regulations and guidelines are contributing to the steady improvement of Web accessibility. There are various accessibility evaluation tools, and they also help Web authors make their pages compliant with guidelines. As a result, an increasing number of Web pages are compliant with the evaluation tools. These days, however, blind people face the serious problem that readingWeb pages is quite difficult. Improvements in information density by using visual effects such as two-dimensional layouts are making it difficult for blind people to understand the page structure. Also, inappropriate alternative texts mislead or confuse blind users. In this paper, to evaluate these kinds of usability problems, we introduce two metrics: navigability and listenability. Navigability evaluates how well structured the Web content is by using headings, intra-page links, labels, etc. Listenability denotes how appropriate the alternative texts are. By using these metrics, we summarize the historical transition of Web usability for blind people.