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Abstract

This W3C Draft Note provides an introduction to use of the Web by people with a variety of disabilities, for the purpose of better understanding their requirements when Web sites and Web-based applications. It is a supporting document for guidelines and technical work of the W3C Web Accessibility Initiative (WAI).

Specifically, this document describes requirements for Web access by people with physical, visual, hearing, and cognitive or neurological disabilities; it describes assistive technologies used by some people with disabilities when accessing the Web; and it provides examples of people with disabilities successfully or unsuccessfully accessing the Web according to the designs of Web sites and Web-based applications. This document is not intended as a comprehensive or in-depth description of disability, nor of assistive technologies used by people with disabilities.

Status of this document

This document is [not yet] a W3C Note made available by the W3C Web Accessibility Initiative. This NOTE has [not yet] been jointly approved by the WAI Education and Outreach Working Group (EOWG), the Web Content Guidelines Working Group, the User Agent Guidelines Working Group, the Authoring Tool Guidelines Working Group, and the Protocols and Formats Working Group (PFWG). This version is offered for EOWG review and has [not yet] been reviewed by all listed editors.

Publication of a W3C Note does not imply endorsement by W3C membership. A list of current W3C technical reports and publications, including working drafts and notes, can be found at http://www.w3.org/TR.

NOTE: This draft has been re-edited through the end of Section one, "How Different Disabilities Affect Access to the Web." Section two is not edited, and section three has not been added yet.

NOTE: This document has been modified after its original date of publishing to correct the "Latest Version" URI.

1. How Different Disabilities Affect Access to the Web

This section describes several general groupings of disabilities, and how they affect access to the Web. There are no universally accepted or absolute categorizations of disability. Disability terminology varies from country to country, and between different disability communities in the same country. Abilities can vary from person to person, or over time, for different people with the same kind of disability. People can have combinations of different limitations, such as a visual and hearing disability together. This particular combination of disabilities is described below.

The term "disability" itself is also used very generally in this document. Many 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. 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 repetitive stress syndrome. There is a trend in some communities away from using medical terminology to describe disability, and a trend in many communities away from using negative terminology or epithets frequently used in the past. This Draft Note does not attempt to comprehensively address these issues of terminology.

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 the commands in browsers and authoring tools, since they both have difficulty using a mouse but can use different assistive technologies to activate commands that are supported by a standard keyboard interface.

The number and severity of disabilities tend to increase as people with age, and may include changes in vision, hearing, memory, or motor function, which can be accommodated on the Web as with any other disabilities.

Many of the accessibility solutions described in this Note contribute to "universal design" or "design for all" by benefiting non-disabled users. For example, support for speech output not only benefits blind users, but also Web users whose eyes are busy with other tasks; while captions of audio not only benefit deaf users but also increase the efficiency of indexing and searching audio content on Web sites.

Solutions for the barriers to Web site accessibility described in this section are available in the Web Content Accessibility Guidelines 1.0. Solutions for browser accessibility are available in the User Agent Accessibility Guidelines, and for authoring tool accessibility in the Authoring Tool Accessibility Guidelines.

Visual Disabilities

Blindness

Blindness involves a substantial uncorrectable loss of vision in both eyes.

To access the Web, most individuals who are blind rely on screen readers (software that reads text on the screen with a synthetic voice) and/or refreshable braille displays (a device that dynamically displays lines of text on the screen in braille). Some people who are blind prefer text-based browsers to graphical browsers.

Barriers that people with blindness may encounter on the Web include:

• images that do not have alt text
• complex images (e.g., graphs or charts) that are not adequately described
• video that is not described in text or audio
• tables that do not make sense when read serially (in a cell-by-cell mode)
• frames that do not have "NOFRAME" alternatives, or that do not have meaningful names
• forms that cannot be tabbed through in a logical sequence, or that are poorly labelled
• browsers and authoring tools that lack keyboard support for all commands
• browsers and authoring tools that do not use standard applications programmer interfaces for the operating system they are based in

Low Vision

There are many types of low vision, including 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 vision.

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 magnification or screen enhancement software. Some individuals prefer specific combinations of text and background colors, such as a 24-point bright yellow font on a black background, or choose certain typefaces that they find especially legible.

Barriers that people with low vision may encounter on the Web include:

• Web pages with absolute font sizes that do not enlarge easily
• Web pages that, because of inconsistent layout, are difficult to navigate when enlarged, due to loss of surrounding context
• browsers that do not support user override of authors' style sheets

Color Blindness

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, people with color blindness may 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:

• color that is used as a unique marker to emphasize text on a Web site
• text that inadequately contrasts with background color or patterns
• browsers that do not support user override of authors' style sheets

Hearing Disabilities

Deafness

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 be fluent readers of a written language.

To use the Web, people who are deaf may rely on captions for audio content.

Barriers that people who are deaf may encounter on the Web include:

• lack of captions or transcripts for audio content on the Web
• lack of visual signposts in pages full of text, which can slow comprehension for non-native readers of a written language

Hard of hearing

A person with a mild to moderate hearing impairment may be considered hard of hearing.

To use the Web, people who are hard of hearing may rely on captions for audio content together with amplification of audio.

Barriers encountered on the Web include:

• lack of captions or transcripts for audio content

Physical Disabilities

Motor

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 further impedes movement. Any of 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 using single keystrokes rather than the simultaneous keystrokes needed to activate commands in some applications. 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:

• browsers and authoring tools that do not support serialized keystrokes for commands
• forms that cannot be tabbed through in a logical order
• interactive forms with time-limited response options

Speech

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 are beginning to 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:

• Web sites that require voice-based interaction and have no alternative input mode

Cognitive and Neurological Disabilities

Learning disabilities

Individuals with learning disabilities may have difficulty processing written language or images when read visually, or spoken language when heard, or numbers when read visually or heard. Specific learning disabilities can affect the ability to focus.

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 speech output to facilitate comprehension, while someone with an auditory learning disability may use captions to help understand an audio track. An individual who is highly distractible 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 learning disabilities may encounter on the Web include:

• lack of alternative modalities for information on Web sites, for instance lack of alternative text that can be converted to audio to supplement visuals, or the lack of captions for audio
• distracting visual or audio elements that cannot easily be turned off
• lack of clear and consistent organization of Web sites

Impairments of intelligence

Some individuals learn more slowly or have difficulty understanding complex concepts.

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.

Barriers include:

• lack of clear or consistent organization of Web sites
• use of unnecessarily complex language on Web sites
• lack of graphics on Web sites

Memory impairments

Individuals may have memory difficulties for a variety of reasons: for instance problems with short-term memory, missing long-term memory, or loss of language.

To use the Web, people with memory impairments may rely on a consistent navigational structure throughout the site, and...

Barriers include:

• lack of clear or consistent organization of Web sites

Seizure disorders

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 turn off animations, blinking text, or audio.

Avoidance of these visual or audio frequencies in Web sites prevents inadvertent triggering of seizures. Barriers include:

• use of visual or audio frequencies that can trigger seizures

Psychiatric disabilities

Individuals with mental or emotional disabilities may have difficulty focusing.

To use the Web, people with psychiatric disabilities may turn off distracting visual or audio elements.

Barriers include:

• lack of clear and consistent organization of a Web sites
• distracting visual or audio elements

[not revised past this point]

2. Tools

The following is a list of assistive technologies that some people with disabilities use to browse the Web. 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 dealing 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.

Alternate keyboards or switches

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 on-screen keyboards, eyegaze keyboards, and sip-and-puff switches. Applications that can be operated entirely from the standard keyboard , with no mouse movements required, support single-switch access or access via alternative keyboards.

Braille and refreshable braille

Braille is a technique involving six to eight dots that are raised in different patterns to represent letters and numbers so that they may be read by people who are blind using their 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) 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 can be raised and lowered dynamically to allow any braille words to be displayed. Only letters and numbers can be represented in braille, although some braille printers have a utility that allows simple graphics to be drawn on a sheet using the raised dots at a resolution of approximately 11 dots per inch.

Screen magnifiers

Software used primarily by individuals with low vision that magnifies a portion of the screen for easier viewing. Note that at the same time screen magnifiers make presentations larger, they also reduce the area of the document that may be viewed. Some screen magnifiers therefore offer two views of the screen: one magnified and one default size for navigation.

Screen readers:

Software used by individuals who are blind or have learning disabilities that interprets what is displayed on a screen, and directs it either to speech synthesis, for audio output, or refreshable braille, for tactile output. Some screen readers use the document tree (i.e., the parsed document) as their input. However, older screen readers make use of the rendered version of a document, meaning that document order or structure may be lost (e.g., when tables are used for layout) and their output may be confusing.

Sound notification

Features of some operating systems 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

Software used by individuals with some physical or cognitive disabilities that highlights or announces selection choices (e.g., menu items, groups of possible phrases, etc.) one at a time. A user selects a desired item by hitting a switch when the desired item is highlighted or announced.

Voice recognition

Voice recognition is used by people with some physical disabilities or temporary injuries to hands and forearms -- as well as some users interested in greater convenience, and as an input method in some voice browsers. Applications that have full keyboard support can be used with voice recognition.

Examples of Accessibility and Inaccessibility on the Web

[Adapt Marja's "scenarios" here]

About the Web Accessibility Initiative

[Edit/update based on CSS boilerplate]

W3C's Web Accessibility Initiative (WAI) addresses accessibility of the Web through five complementary activities that:

1. Ensure that the technology of the Web supports accessibility
2. Develop accessibility guidelines
3. Develop tools to facilitate evaluation and repair of Web sites
4. Conduct education and outreach
5. Conduct research and development

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 for Disabled and Elderly Programme; IBM, Lotus Development Corporation, and NCR.

Additional information on WAI is available at http://www.w3.org/WAI.

About the WAI Web Accessibility Guidelines

[Edit/update]

Web accessibility guidelines are essential for Web site development and for Web-related applications development. WAI is coordinating with many organizations to produce three sets of guidelines:

• "Web Content Accessibility Guidelines", W. Chisholm, G. Vanderheiden, and I. Jacobs, eds. These guidelines explain how to design accessible Web content.
• "Authoring Tool Accessibility Guidelines", J. Treviranus, J. Richards, I. Jacobs, C. McCathieNevile, eds. These guidelines explain how to build accessible Web authoring tools.
• "User Agent Accessibility Guidelines", J. Gunderson and I. Jacobs, eds. These guidelines explain how to design accessible user agents (browsers, multimedia tools, assistive technologies, etc.)

About the World Wide Web Consortium (W3C)

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 MIT Laboratory for Computer Science (LCS) 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. To date, more than 320 organizations are Members of the Consortium. For more information about the World Wide Web Consortium, see http://www.w3.org/

Contributors

Gregg Vanderheiden, Kate Vanderheiden, [add EOWG once reviewed, other WAI groups once reviewed]

References

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