John has cerebral palsy and his coordination limitations prevent him from using a mouse. Jean is blind and a mouse is pointless. Jane, who is deaf, cannot use sound cues, audiotracks, etc.. Joan has a reading disability and finds it difficult to read plain text. John is adept at using his alternative keyboard to drive his computer. The keys are bigger and have more space between them than on a standard keyboard. Jean uses a standard keyboard but instead of displaying pages visually on a standard monitor; he listens to page text read by a speech synthesizer. Jane uses a graphical desktop computer, but requires captions to understand movies she downloads from the Web. Joan also uses software that reads text from the screen aloud and highlights which word is being read. This way, she can see and hear the words.
Presenting information in a variety of media allows people to select one or multiple media presentations that are most appropriate for them. You can design rich multimedia pages that look good and are also accessible by Jean, Jane, John, Joan and other users with disabilities. By ensuring that users may interact with a page using either mouse or keyboard, it is possible for users with a wide range of disabilities to surf the Web. If you ensure that information presented in sound is also available
through other means, you ensure that people who are deaf or hard of hearing can use your sites. By using well-designed, rich multimedia presentations, you help facilitate understanding for users with cognitive and learning disabilities. These design tips, help all Web site visitors, not just those with disabilities.
Which Disabilities Affect Web Access?
In the field of accessible design, disabilities may be organized into 4 major categories: physical, cognitive and learning, visual, and auditory. Each of the categories can be refined according to the severity of the disability. People who are legally blind (20/200 in the better eye after correction or whose field of vision is less than 20 degrees) may have some vision. They may be able to distinguish between light and dark; they may have only peripheral vision; or they may have very blurry vision.
Disabilities can occur suddenly, as with an injury, or progressively as with some diseases or the aging process. Many people are born with disabilities. Situational or technological constraints can cause a person to use access methods that are common to users with disabilities. For example, a person accessing the Web while driving his car can use his hands or eyes, and must instead use speech synthesis & recognition.
People often have disabilities from one or more of the major categories. Many people older than 65 experience hearing and vision loss, as well as reduced mobility.
Physical disabilities include impairments of the muscles and skeletal system. Mobility, and dexterity may be difficult due to weak or paralyzed muscles,
involuntary extra movement, or missing limbs. This may make using a mouse difficult or impossible, for a pointing device needs good hand-eye coordination. Impaired mouth or facial muscles may result in speech impairments, making it difficult for those with such disabilities to use speech recognition technologies.
Those with similar abilities can use an alternative keyboard. Clara, who can't use her hands but can move her legs, torso, and head, can use a mouth stick to press keys on the keyboard, and can simulate mouse movements using head pointers. People with clear speech can use speech recognition technologies to enter data and operate software. Finally, those with very limited mobility, can use a combination of hardware switches, scanning software, and other devices that control their computers through raising eyebrow or tapping a toe.
Since these devices can simulate mouse and keyboard input, making pages accessible via mouse and keyboard will enable users of most assistive hardware and software to access information. Test your pages to see if they can be used without a mouse to ensure that they are keyboard accessible. Pages should use client-side image maps rather than server-side images, so that the browser will interpret the regions of the imagemap. Otherwise, the browser will recognize only the single image and will not connect to the link associated with the region's hot spots. You should also ensure that functionalities available through mouse-specific events like "onmouseclick" are also available through alternative keyboard inputs.
Auditory disabilities are impairments of the ear or neural functions associated with hearing that range in severity from hearing loss that may be corrected with a hearing aid to hearing muffled sounds only to hearing no sound at all.
Make pages accessible to the disabled. Ensure that all important information presented through sound is available to other senses. Movie sound tracks should be accompanied by text transcripts. Better yet, sound tracks should be accompanied by captions synchronized with the movie. Captions should include descriptions of important sounds, such as a honking horn, which would not be detectable by watching the video alone.
Like auditory disabilities, visual disabilities vary in severity. These Web site visitors may experience blindness, low vision, color deficiencies, and so on. The visual disabled rely on sound, touch, and sometimes limited visual input. Screen reader software sends document or page text to speech synthesizers or dynamic braille displays. Screen readers make it easier to navigate documents that are highly structured. Use markup to structure the documents rather than relying on visual cues alone to communicate structure. Style sheets allow Web site visitors to override author-specified styles. Users with low vision need large fonts and can configure their browsers.
To accommodate these Web site visitors, provide textual equivalents for non-textual information, including images, video clips and sounds. This provides visitors with visual disabilities, and those with auditory disabilitiesan alternative way to interact with the page. By providing textual equivalents, you go a long way towards making your pages accessible to most of the disabled. This doesn't mean providing separate text-only pages, which can result in having to make and update text only versions of every single page on the site. Instead, it's a good idea to build alternatives directly into the main pages.
Web site visitors can read your pages, ensure that your pages work without a mouse, that information presented in color is not presented through color alone, and that important information that is rendered visually is available to other senses. To test the accessibility of your page to the visually disabled, view it without graphics, printed, or on a black and white screen. Another way to verify your pages' accessibility is to read them out loud or over the phone to a colleague.
Cognitive and Learning Disabilities
Cognitive disabilities include a variety of brain or neural disorders arising congenitally or as a result of trauma. People with these disorders may have difficulty remembering, reading or writing, maintaining focus, learning, or have other difficulties with understanding and cognition.
Some disabled, including those with dyslexia and other reading difficulties, find text-to-speech useful. People who have difficulty writing find speech recognition and word prediction software useful. They may find alternative keyboards to be helpful, since these keyboards can be simplified or can use pictures instead of letters. Although visual and auditory information is available to people with cognitive and learning disabilities, they may not be able to make sense of it.
As a Web designer, you can help by organizing pages consistently and predictably. Provide navigation mechanisms such as navigation bars. Present information through more than one mode: pictures, text, sounds, graphics, and so on.
A variety of people access the Web who have disabilities and use various tools to help them access the Web. But some sites do not work with these tools and are inaccessible. Web designers can make sites that are rich in multimedia that are also accessible to the disabled. Sites designed to account for these users will likely be more usable to all Web users.
Ian Jacobs contributed to this article.