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This W3C Working Draft provides an introduction to use of the Web by people with a variety of disabilities, for the purpose of better understanding their user requirements when using Web sites and Web-based applications. This document provides supporting information for guidelines and technical work of W3C's Web Accessibility Initiative (WAI). It is not intended as a comprehensive or in-depth description of disabilities, nor of assistive technologies used by people with disabilities.
Specifically, this document:
This section describes the status of this document at the time of its publication. Other documents may supersede this document. The latest status of this document series is maintained at the W3C.
This document is a W3C Working Draft intended for eventual publishing as a W3C Note. It is issued by the Education and Outreach Working Group (EO WG) for review by EO WG members. Comments from the public and W3C Members and working groups are also welcome, at firstname.lastname@example.org. It is produced as part of the Web Accessibility Initiative International Program Office Activity.
A list of current W3C technical reports and publications, including working drafts and notes, can be found at http://www.w3.org/TR.
The Web Accessibility Initiative develops accessibility guidelines for Web sites and for browsers and authoring tools in order to make it easier for people with disabilities to use the Web. Given the Web's increasingly important role in society, this access to the Web is vital for people with disabilities. Many accessibility features also benefit Web users who do not have disabilities.
This document provides a general introduction on how people with different kinds of disabilities use the Web, as background for the technical provisions described in the Web Content Accessibility Guidelines 1.0, Authoring Tool Accessibility Guidelines 1.0, and User Agent Accessibility Guidelines 1.0.
This section describes general kinds of disabilities that can affect access to the Web. There are as yet no universally accepted or absolute categorizations of disability, despite efforts by some organizations to move towards that goal.
Commonly used disability terminology varies from country to country, and between different disability communities in the same country. There is a trend in some communities away from using medical terminology and/or negative terminology to describe disability. This document does not attempt to comprehensively address these issues of terminology.
Abilities can vary from person to person, or over time, for different people with the same type of disability. People can have combinations of different limitations, such as a visual and hearing disability together.
The term "disability" is used very generally in this document. Some people with conditions described below would not consider themselves to have disabilities. They may, however, have limitations related to sensory, physical or cognitive functioning which can affect access to the Web. These limitations can include injury-related and aging-related conditions, and can be temporary or chronic. An example of an injury-related limitation that is temporary for some people and chronic for others is repetitive stress injury.
The number and severity of limitations tend to increase as people age, and may include changes in vision, hearing, memory, or motor function, which can be accommodated on the Web as with any other disabilities.
Different disabilities sometimes require similar accommodations. For instance, both someone who is blind ,and someone who cannot use his or her hands, require full keyboard support for commands in browsers and authoring tools, since they both have difficulty using a mouse but can use assistive technologies to activate commands that are supported by a standard keyboard interface.
Many of the accessibility solutions described in this document contribute to "universal design" or "design for all" by benefiting non-disabled users as well as people with disabilities. For example, support for speech output not only benefits blind users, but also Web users whose eyes are busy with other tasks; while captions for audio not only benefit deaf users, but also increase the efficiency of indexing and searching for audio content on Web sites.
Blindness involves a substantial, uncorrectable loss of vision in both eyes.
To access the Web, many individuals who are blind rely on screen readers -- software that reads text on the screen (monitor) and outputs this information to a speech synthesizer and/or refreshable braille display (a device that dynamically displays lines of text on the screen in braille). Some people who are blind use text-based browsers such as Lynx instead of the graphical user interface browser plus screen reader. They may use navigation strategies such as tabbing through the headings or links on a Web page, rather than reading every word in linear order.
Examples of barriers that people with blindness may encounter on the Web include:
There are many types of low vision, for instance poor acuity (vision that
is not sharp), tunnel vision (seeing only the middle of the visual field),
central field loss (seeing only the edges of the visual field), and clouded
To use the Web, some people with low vision use extra-large monitors, and increase the size of system fonts and images. Others use screen magnifiers or screen enhancement software. Some individuals use specific combinations of text and background colors, such as a 24-point bright yellow font on a black background, or choose certain typefaces that are especially legible for their particular vision requirements.
Barriers that people with low vision may encounter on the Web include:
Color blindness is a lack of sensitivity to certain colors. Common forms
of color blindness include difficulty distinguishing between red and green,
or between yellow and blue. Sometimes color blindness results in the inability
to perceive any color.
To use the Web, some people with color blindness use their own style sheets to override the font and background color choices of the author.
Barriers that people with color blindness may encounter on the Web include:
Deafness involves a substantial uncorrectable impairment of hearing in both
ears. Some deaf individuals' first language is a sign language, and they
may or may not read or speak a language fluently.
To use the Web, many people who are deaf rely on captions for audio content. They may need to toggle the captions on an audio file on or off as they browse a page.
Barriers that people who are deaf may encounter on the Web include:
A person with a mild to moderate hearing impairment may be considered hard
To use the Web, people who are hard of hearing may rely on captions for audio content and/or amplification of audio. They may need to toggle the captions on an audio file on or off, or adjust the volume of an audio file.
Barriers encountered on the Web include:
Motor disabilities can include weakness, limitations of muscular control
(such as involuntary movements, a lack of coordination, or paralysis),
limitations of sensation, joint problems, or missing limbs. Some physical
disabilities can include pain which impedes movement. These conditions can
affect the hands and arms, as well as other parts of the body.
To use the Web, people with disabilities affecting the hands or arms may use a specialized mouse; a keyboard with a layout of keys that matches their range of motion; a head-mouse, head-pointer, or mouth-stick; voice-recognition software; an eye-gaze system, or other assistive technologies to access and interact with the information on Web sites. They may activate commands by typing single keystrokes with a pointer, rather than typing simultaneous keystrokes ("chording") to activate commands. They may need more time when filling out interactive forms on Web sites.
Barriers that people with motor disabilities affecting the hands or arms may encounter include:
Speech disabilities can include difficulty producing speech that is recognizable
by some voice recognition software, either in terms of loudness or clarity.
To use parts of the Web that rely on voice recognition, someone with a speech disability needs to be able to use an alternate input mode such as text entered via a keyboard.
Barriers that people with speech disabilities encounter on the Web include:
Individuals with dyslexia or dyscalculia (sometimes called "learning
disabilities" in the U.S.) may have difficulty processing written language
or images when read visually, or spoken language when heard, or numbers when
read visually or heard.
To use the Web, people with learning disabilities may rely on getting information through several modalities at the same time. For instance, someone who has difficulty reading may use a screen reader plus synthesized speech to facilitate comprehension, while someone with an auditory processing disability may use captions to help understand an audio track.
Barriers that people with learning disabilities may encounter on the Web include:
Individuals with attention deficit disorder may have difficulty focusing on information.
To use the Web, an individual with an attention deficit disorder may need to turn off animations on a site in order to be able to focus on the site's content.
Barriers that people with attention deficit disorder may encounter on the Web include:
Individuals with impairments of intelligence (sometimes called "learning
disabilities" in Europe) may learn more slowly, or have difficulty understanding
To use the Web, people with impairments of intelligence may take more time on a Web site, may rely more on graphics to enhance understanding of a site, and may benefit from the level of language on a site not being unnecessarily complex for the site's intended purpose.
Individuals with memory impairments may have problems with short-term memory,
missing long-term memory, or some loss of language.
To use the Web, people with memory impairments may rely on a consistent navigational structure throughout the site.
Individuals with mental or emotional disabilities may have difficulty focusing
on information on a Web site, or difficulty with blurred vision or hand tremors
due to side effects from medications.
To use the Web, people with psychiatric disabilities may need to turn off distracting visual or audio elements, or to use screen magnifiers.
Some individuals with seizure disorders are triggered by visual flickering
or audio signals at a certain frequency.
To use the Web, people with seizure disorders may need to turn off animations, blinking text, or certain frequencies of audio. Avoidance of these visual or audio frequencies in Web sites prevents inadvertent triggering of seizures.
Changes in people's functional ability due to aging can include subtle and/or gradual changes in a combination of abilities, including vision, hearing, dexterity and memory. Any of these can affect an individual's ability to access Web content; however, together these changes can become more complex to accommodate. For example, someone with low vision may need screen magnification, however the user loses surrounding contextual information when using screen magnification, which may further hinder an individual who also has limited short-term memory. Barriers can include any of the issues already mentioned above.
Other combinations of disabilities may reduce the user's flexibility in selecting accommodations. For instance, while someone who is blind can benefit from an audio description of the content of a Web-based video, someone who is both deaf and blind would need access to a text transcipt of the description of the video content, which they would could then access via a refreshable braille display. Similarly, someone who is deaf and who also has low vision can benefit from captions on audio files, but would need to be able to enlarge the caption display.
Assistive technologies are products used by people with disabilities to help accomplish tasks that they cannot accomplish otherwise or could not do easily otherwise. When the term is used with the Web, assistive technologies usually refer to adaptive software, specially designed hardware devices, and/or standard devices used in alternative ways to provide access for people with disabilities. Some assistive technologies rely on output of other user agents, such as graphical desktop browsers, text browsers, voice browsers, multimedia players, plug-ins. This is not a comprehensive list.
Alternate keyboards or switches are hardware or software devices used by people with physical disabilities, that provide an alternate way of creating keystrokes that appear to come from the standard keyboard. Examples include keyboard with extra-small or extra-large key spacing, keyguards that only allow pressing one key at a time, on-screen keyboards, eyegaze keyboards, and sip-and-puff switches. Web-based applications that can be operated entirely from the keyboard, with no mouse required, support a wide range of alternative modes of input.
Braille is a system using six to eight raised dots in various patterns to represent letters and numbers that can be read by the fingertips. Braille systems vary greatly around the world. Some "grades" of braille include additional codes beyond standard alpha-numeric characters to represent common letter groupings (e.g., "th," "ble" in Grade II American English braille) in order to make braille more compact. An 8-dot version of braille has been developed to allow all ASCII characters to be represented. Dynamic or refreshable braille involves the use of a mechanical display where dots (pins) can be raised and lowered dynamically to allow any braille characters to be displayed.
Screen magnification is software used primarily by individuals with low vision that magnifies a portion of the screen for easier viewing. At the same time screen magnifiers make presentations larger, they also reduce the area of the document that may be viewed, removing surrounding context . Some screen magnifiers offer two views of the screen: one magnified and one default size for navigation.
Software used by individuals who are blind or who have dyslexia that interprets what is displayed on a screen and directs it either to speech synthesis for audio output, or to refreshable braille for tactile output. Some screen readers use the document tree (i.e., the parsed document code) as their input. Older screen readers make use of the rendered version of a document, so that document order or structure may be lost (e.g., when tables are used for layout) and their output may be confusing.
Sound notification is an alternative featuresof some Web-based applications that allow deaf or hard of hearing users to receive visual notification that a warning or error sound has been emitted by the computer.
Scanning software is adaptive software used by individuals with some physical or cognitive disabilities that highlights or announces selection choices (e.g., 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.
Voice recognition is used by people with some physical disabilities or temporary injuries to hands and forearms as an input method in some voice browsers. Applications that have full keyboard support can be used with voice recognition.
The following composite examples show people with a variety of disabilities using assistive technology or adaptive strategies to access the Web. These scenarios do not represent actual individuals.
Ms. Laitinen is an adjuster at an insurance company. She is completely blind. She uses a screen reader to interpret what is displayed on the screen and drive a combination of speech output and braille output. She uses the speech output for rapid review of the text in a document, and has become accustomed to listening to speech output at a speed that her co-workers cannot understand at all. She uses the refreshable braille output to check the exact wording of text since braille gives a more precise rendering of what is on a page.
[@@provide detail: form- and frame-based navigation. table unwrapping. non-html formats. separate of content, user agent issues. standardization across department]
Mr. Lee is a reporter who must type his articles to publish in an on-line journal. Over his twenty-year career he has developed repetitive stress injury (RSI) in his hands and arms, and it has become painful for him to type. He uses voice recognition to dictate his articles.
[@@review detail, change tone] Mr. Lee has difficulty using the same editing tool and site management set as his colleagues, because these applications are missing some of the keyboard equivalents for mouse-driven commands. To activate any commands that do not have keyboard equivalents, he must use the mouse with his hand instead of using speech recognition. He finds after several months that he is making no progress on healing the original RSI, since he is continually re-aggravating the his hand muscles by his intermittent mouse use.
Mr. Hernandez is taking several "distance learning" courses in engineering. He is completely deaf.
[@@adjust detail, change tone] He had no trouble with the curriculum until the university upgraded their on-line courseware to a multimedia approach. Suddenly he found that he cannot follow up to half of the instructional material, and his performance in the class started to slip. After receiving complaints from several students with similar problems, the university looked into multimedia formats that support accessibility, and settled on a SMIL-based application that includes support for captioning of audio and description of video.
Ms. Ishikawa attends middle school and particularly likes her science class. She has dyslexia which leads to substantial difficulty reading.
[@@provide more technical detail] The school she attends has started to use more and more on-line curriculum to supplement the textbooks in class, and she is worried about keeping up with the additional reading load. She tries out screen reading software with speech synthesis and finds that she is able to read along visually with the text much more easily when she can also hear some of it read to her with the speech synthesis. Since the on-line curriculum has been designed for accessibility, she is able to do this smoothly and to keep up with her class.
Mr. Johnson is considering buying some new music over the Web. He has one of the most common visual disabilities for men: color blindness, which for him means he cannot distinguish between green and red.
Mr. Johnson notices that he has difficulty reading many of the music sites, and wonders if it might be due to his color blindness. He uses his browser settings to turn off the site's style sheets and substitute his own style sheet, which he has configured to provide the optimal contrast he needs. He is then able to read the sites easily.
Ms. Smith uses the Web to find new restaurants to go to with friends and colleagues. She has low vision and no hearing. She uses a screen magnifier to enlarge the text on Web sites until she can read it, but sometimes that isn't sufficient so she also uses a screen reader to drive a refreshable braille display, which she reads slowly. When she is using the screen magnifier, she also uses her browser settings to turn off the background color and patterns because otherwise there is not enough contrast for her.
[@@review/expand detail] The city Ms. Smith lives in has compiled a multi-media virtual tour of entertainment options in the area, and Ms. Smith discovers it has been completely captioned and described. She takes the on-line tour, slowing it down a few times while she uses a combination of braille and screen magnification. Then she sends the URI of the virtual tour to friends, to see if they share her interest in trying a particularly good-looking new restaurant downtown that weekend.
Mr. Todd uses the Web to review his stock portfolio and manage his retirement funds. He has some short-term memory loss, low vision, and a hand tremor.
[@@review/expand detail] He customized his portfolio window to give a streamlined portfolio view, and to automatically check certain stock performance critieria since he has difficulty remembering how to find the information otherwise. He uses his browser settings to enlarge the font on the site so it is easier for him to see. While the icons on the site do not enlarge along with the fonts, they are large enough already that he can not only see them easily, but can select them with the mouse even when his hand is trembling .
The World Wide Web is full of information about disabilities. The key can be locating information that is relevant to the issue of accessibility to the Web, accurate, and up-to-date. It can be important to note the perspective from which the information is written. For example, there is much information about different diseases on the Web, but medical details can be less relevant to understanding how people with disabilities use the Web than the perspectives of people with disabilities themselves, as well as that of organizations that focus on accessibility strategies for using information technologies and telecommunications.
W3C's Web Accessibility Initiative (WAI) addresses accessibility of the Web through five complementary activities that:
WAI's International Program Office enables partnering of industry, disability organizations, accessibility research organizations, and governments interested in creating an accessible Web. WAI sponsors include the US National Science Foundation and Department of Education's National Institute on Disability and Rehabilitation Research; the European Commission's DG XIII Telematics Applications Programme for Disabled and Elderly; Government of Canada, Industry Canada; IBM, Lotus Development Corporation, Microsoft, and Verizon. Additional information on WAI is available at http://www.w3.org/WAI.
The W3C was created to lead the Web to its full potential by developing common protocols that promote its evolution and ensure its interoperability. It is an international industry consortium jointly run by the Laboratory for Computer Science (LCS) at Massachusetts Institute of Technology (MIT) in the USA, the National Institute for Research in Computer Science and Control (INRIA) in France and Keio University in Japan. Services provided by the Consortium include: a repository of information about the World Wide Web for developers and users; reference code implementations to embody and promote standards; and various prototype and sample applications to demonstrate use of new technology. As of October 2000, over 450 organizations are Members of the Consortium. For more information about the World Wide Web Consortium, see http://www.w3.org/.
We would like to thank the following people who have contributed substantially to this document:
Ian Jacobs, Marja-Riitta Koivunen, Gregg Vanderheiden, Kate Vanderheiden, and Members of the Education and Outreach Working Group.
[@@ review, expand]