Support for web authors
Understanding the need for accessible web design
Contents of this page:
See elsewhere:
Disabilities and difficulties affecting internet
usage
Computer technology and the internet have a tremendous potential to broaden
the lives and increase the independence of people with disabilities. However,
five types of disabilities can affect Internet usage:
- Visual Difficulties (blindness, low vision, colour-blindness)
- Hearing Difficulties (deafness, deaf-blindness)
- Mobility Difficulties
- Specific Learning Difficulties (Reading disorders such as dyslexia,
learning disorders, short-term memory deficit, Downs Syndrome, Alzheimer's
Disease, etc.)
- Seizure Disorders (epilepsy etc)
According to the World Health Organization, more than 750 million people
worldwide have a disability. 15% of people age 22 to 44 have a disability, and
statistically, most people during their lifetime will have a disability or
experience a limitation that will temporarily or permanently affect their lives.
Accommodating individual needs
Visual difficulties
People with visual disabilities are individuals who are blind, have low
vision, or have colour blindness. People who are blind need text equivalents for
the images used on the web page, because they and their assistive screen reader
technology cannot obtain the information from the image. A person who has a
visual disability will not find the mouse useful because it requires hand and
eye coordination. Instead, this person must navigate the web page using only the
keyboard
The needs of people with poor sight vary considerably, depending on how their
eye condition affects their vision. Some people require large text, while others
can read only smaller letters. Some need the assistance of a hardware or
software magnifier to enlarge the text beyond simple font enlargement. Most need
a highly contrasting colour scheme, and some have very specific needs, for
example yellow text on a black background. Synthesised speech software can read
the content of web pages aloud through a speaker, while braille software can
output the same content to a retractable braille display so that the web page
can be read by touch.
About 8 percent of men and 0.5 percent of women have some form of colour
blindness; for some websites that could translate to 1 in 12 visitors. When
information is presented by colour alone, a person who is colour blind misses
that information.
To cater for everyone, websites should allow individual users to customise
their web browser to adjust the text and colour settings to suit their own
particular needs and circumstances.
Many visual difficulties are relatively simple for a web author to
accommodate.
Hearing difficulties
When using audio or video on a website, remember that people who are deaf or
hard of hearing require visual representations of auditory information provided.
Solutions for this include:
- Use of closed captioning (subtitles)
- Use of blinking error messages
- Use of visual text transcripts of the spoken audio.
Interfaces should not depend on the assumption that users can hear an
auditory notice. In addition to users who have hearing difficulties, users sitting in
noisy offices, or in public places where sound must be turned off also need the
visual notification.
Some users can only hear audible cues at certain frequencies or volumes.
Volume and frequency of audio feedback should be easily configurable by the
user.
Mobility difficulties
Many Internet users have some degree of motion difficulty (some are unable
to use a mouse, or can not direct a mouse pointer easily; others use assistive
technology to operate special input devices). Site navigation is obviously
more difficult for motion-impaired readers, but a carefully designed website can
accommodate these readers.
- Provide amply-sized hyperlinks (or their graphical counterparts) for
navigation.
- Avoid the need for chorded key-presses (more than one key at a time).
- Image maps are not advised, unless supported by alterative text based
links.
- Don't require users to be able to click on a moving target in order to
proceed to another page.
- Offer additional plain text links.
- Give thought to the TAB order of the various links and form elements on
the page.
Specific learning difficulties
To use the web, people with learning disabilities may rely on getting
information through several media at the same time. For instance, someone who
has difficulty reading may use a screen reader plus synthesized speech to aid
comprehension; or someone with an auditory processing disability may use closed
captioning (subtitles) to help them to understand an audio track.
People with specific cognitive or learning disabilities, such as dyslexia and
short-term memory deficit, need more general solutions, which include providing
a consistent design and using simplified language.
- Use templates to set the same layout and design for each page, so a person
with a learning disability can more easily navigate through a website.
- Provide multimedia elements in other forms, (such as providing both an
audio file and a transcript of a video). By simultaneously viewing the text
and hearing it read aloud, users can take advantage of both auditory and
visual skills to comprehend the material better.
Seizure disorders
Displays which flicker or flash can cause photosensitive epileptic seizures
in susceptible individuals, particularly if the flash has a high intensity and
is within the frequency range between 2 Hz and 55 Hz. This includes flashing
text, turning graphics on and off or repeatedly changing between different
images on the screen.
- Generally the rule is to avoid causing content to blink, flicker, or
move.
As browsers cannot be configured to stop the refreshing of pages, do not
create pages that periodically auto-refresh.
- If flashing content on your web page cannot be avoided then:
1. Minimize the area of the screen which is flashing. Smaller areas are less
likely to cause seizures.
2. Avoid flashing which has a high level of contrast between the states.
Some individuals are more susceptible to high intensity flashing.
What are assistive technologies?
Assistive technologies are products used by people with disabilities to help
accomplish tasks that they cannot accomplish otherwise or could not do easily
otherwise. Some assistive technologies rely on output of other user agents, such
as graphical desktop browsers, text browsers, voice browsers, multimedia
players, plug-ins. Adaptive strategies may be techniques that people with
disabilities use, with or without assistive technologies, to assist in
navigating web pages. In addition to the descriptions below, this web page lists
the assistive technologies available for on-campus
computer users. See elsewhere: Guidelines for
accessible web design.
Braille display
Users: Low vision and blind users.
Provides line-by-line braille display of on-screen text
using a series of pins to form braille symbols that are constantly updated
as the user navigates through the interface.
Mouth stick or a head wand
Users: Users with mobility difficulties.
Allows user to access the keyboard
'Puff-and-sip' switches / other switches
Users: Users with mobility difficulties.
Often installed on wheelchairs, and have
limited-functionality, these emulate the functionality of the standard
keyboard, to one degree or another.
Scanning software
Users: Users with mobility difficulties, and those with specific
learning difficulties.
Scanning highlights or announces selection choices (eg
menu items, links, phrases) one at a time. A user selects a desired item
by hitting a switch when the desired item is highlighted or announced.
Screen magnification
Users: Low vision and blind users.
Provides magnification of a portion or all of a screen,
including graphics and windows as well as text. Allows users to track
position of the input focus.
Screen reader software
Users: Low vision and blind users plus some users with specific
learning difficulties.
Allows users to navigate through windows, menus, and controls while receiving
text and limited graphics information through speech output or braille display.
'Sound notification'
Users: Users with hearing difficulties.
An alternative feature of some web-based applications that
allows deaf or hard of hearing users to receive visual notification that a
warning or error sound has been emitted by the computer.
Speech recognition
Users: Users with mobility difficulties, and some with specific
learning difficulties.
Speech (or voice) recognition is used as an input method in
some voice browsers.
Tabbing through structural elements
Users: Low vision and blind users, some users with specific learning difficulties,
plus users of text-only browsers.
People who cannot use a mouse, may use the adaptive strategy of using the tab
key for rapidly scanning through links, headers, list items, or other structural
items on a web page.
Text browsers
Users: Low vision and blind users plus users with low bandwidth
connections or non-windows operating systems.
Text browsers such as Lynx are an alternative to graphical
user interface browsers. They can be used with screen readers for people
who are blind.
Text to speech
Users: Low vision and blind users plus some users with specific
learning difficulties.
Translates electronic text into speech via a speech
synthesizer.
Voice browsers
Users: Low vision and blind users, users with mobility difficulties,
plus some users with specific learning difficulties.
Voice browsers allow voice-driven navigation, some with both
voice-input and voice-output, and some allowing telephone-based web
access.