Specific disabilities

Speech disabilities

Some conditions which produce motor disabilities may also produce speech disability eg cerebral palsy, where speech may become slurred owing to a slower response of the muscles controlling the voice. It may then become difficult for voice recognition software to recognize commands. Web sites that require voice-based interaction, and that provide no alternative means of input, would effectively be inaccessible to users with such a disability.

All website functionality should be accessible from the keyboard where other assistive technology may offer greater access.

Jakob Nielsen, in Chapter 6 of Designing Web Usability, predicts that voice activated user interfaces will increase where keyboard use is awkward. If speech is the primary or only input modality to an application, such as possible future online chat systems, then for accessibility issues to be addressed, such an application should retain input via typed text. This also has benefits to users who do not have a speech disability as it provides them a means of entering input which is best rendered as text eg URLs, and so is part of Universal Design.

Try not to rely on a single means of input.

Aging-related disabilities

Those of us who plan to be around for a few more years also have personal reasons to promote accessibility because as we get older, we will experience more disabilities ourselves…It’s definitely worth remembering what awaits us as we get older. Let’s design a world that will be good for us.
Jakob Nielsen Designing Web Usability Chapter 6 Accessibility for Users with Disabilities

As we get older we might expect gradual changes in our our vision, hearing, memory, and/or detexterity, any of which may lead to problems with the way in which we use our computers or other technology. When any of these changes occur in combination accessibility problems are compounded.

For example, someone with low vision may need screen magnification, however when using screen magnification the user loses surrounding contextual information, which adds to the difficulty which a user with short-term memory loss might experience on a Web site. W3

Even so the w3 suggest that

Aging-related conditions can be accommodated on the Web by the same accessibility solutions used to accommodate people with disabilities. W3

There are, of course, a great many assistive technologies for each individual disability.

To take but one example; problems of manual dexterity. Designers of web pages need to keep in mind that many of the assistive technologies mitigating problems with manual dexterity, work through the keyboard or emulate the functionality of the keyboard:

Knowing this, developers can focus on making their content accessible to the keyboard, and ensure that the site is navigable with as few keystrokes as possible. WebAim