Accessibility and usability are two tightly intertwined concepts. The first important relationship is that increased accessibility for users with disabilities almost always leads directly to improved usability for all users. Guideline number one for all user interface design has always been simplicity. This is true whether designing for blind users, old users, children, international users, mobile users, soldiers on the battlefield, or even the average business executive accessing a Web site or the company intranet on a laptop over a slow modem line from a hotel room during a business trip. Simplicity helps everybody.
Going beyond simplicity, the primary goal of the specific accessibility guidelines discussed in this book may be to help users with disabilities, but most of the guidelines will also improve usability for many other groups of users.
The second significant connection between accessibility and usability is the importance of focusing on the performance, ease of use, and ease of learning for actual users when designing Web sites to accommodate users with disabilities. It is not enough that users are capable of accessing a Web site or intranet. It must also be easy, fast, and pleasant to do so, and the interaction must minimize the probability for user error. If you can get in but it's a pain to be there, then users will not feel welcome. It's better to be allowed in than to be kept out, but it's even better when the user experience during the visit is pleasant and productive.
In a study my group conducted recently, we found that current Web sites are three times harder to use for people with disabilities than for our control group of users without disabilities. (Details are at http://www.nngroup.com/reports, from which you can download the full report.)
A second study of senior citizens had a less dramatic but still remarkable outcome: current Web sites are twice as difficult for people older than 65 years to use than for younger users. (You can find details at the Web page mentioned above.) The seniors in our study were not disabled in the traditional sense of the word, and they certainly were able to access the Web sites in the sense that they could get the pages to display, yet the complexity of the designs created major obstacles for them.
If we could get Web designers to consider accessibility as a design goal from the beginning, we could help users in many categories become much more productive in their use of Web sites and intranets without adding to the expense of constructing the design. In fact, simpler designs are often cheaper to build, though they may take more up-front thinking and creativity to plan.
I particularly like the user experience case studies in this book. Reading through these chapters gives great insight into the frustrations users feel when they come across designs that are difficult or impossible to use. I encourage you to read the case studies, but I encourage you even more to conduct similar tests of your own designs.
User testing is quite simple to do and always reveals a long list of changes that will improve a design and increase its business value dramatically. Conducting a usability evaluation with users with disabilities is slightly more complex than running a traditional user-testing session because of the need to allow each user to employ the assistive technology to which he or she is accustomed. But it's not that hard: you can go to the users' offices or homes and use their existing setups. The key elements of user testing remain the same. First, get hold of real users your customers for a Web site or your employees for an intranet. Second, have them sit by the computer and access your design while they perform representative tasks. Ask the users to think out loud so you can find out how they react to each design element and why they take certain paths through the user interface. The third point may be the hardest: you have to shut up and let the users do the talking. Even when they really don't like your site. It's better that you learn this in a study rather than after you have released a design that will hurt your reputation and cost you lost business. Ultimately, the lessons of this book should increase your understanding of the importance of the user experience and provide you with practical resources to improve that experience for everyone who visits the sites you create.
Jakob Nielsen, Ph.D.
Nielsen Norman Group
Mountain View, CA