How People with Disabilities Use the Web

							How People with Disabilities
      Use the Web

    Due to WAI of W3C.ORG
          Judy Brewer
       Scenarios of People with
       Disabilities Using the Web

• Please note that the scenarios do not represent actual individuals,
  but rather individuals engaging in activities that are possible using
  today's Web technologies and assistive technologies.
• The reader should not assume that everyone with a similar disability
  to those portrayed will use the same assistive technologies or have
  the same level of expertise in using those technologies.
• In some cases, browsers, media players, or assistive technologies
  with specific features supporting accessibility may not yet be
  available in an individual's primary language.
• Disability terminology varies from one country to another, as do
  educational and employment opportunities.
                            Scenarios
•   online shopper with color blindness (user control of style sheets)
•   reporter with repetitive stress injury (keyboard equivalents for mouse-driven
    commands; access-key)
•   online student who is deaf (captioned audio portions of multimedia files)
•   accountant with blindness (appropriate markup of tables, alternative text,
    abbreviations, and acronyms; synchronization of visual, speech, and braille
    display)
•   classroom student with dyslexia (use of supplemental graphics; freezing
    animated graphics; multiple search options)
•   retiree with aging-related conditions, managing personal finances
    (magnification; stopping scrolling text; avoiding pop-up windows)
•   supermarket assistant with cognitive disability (clear and simple language;
    consistent design; consistent navigation options; multiple search options)
•   teenager with deaf-blindness, seeking entertainment (user control of style
    sheets; accessible multimedia; device-independent access; labelled frames;
    appropriate table markup)
     Online shopper with color
             blindness

• Mr. Lee wants to buy some new clothes,
  appliances, and music.
• As he frequently does, he is spending an
  evening shopping online.
• He has one of the most common visual
  disabilities for men: color blindness, which
  in his case means an inability to
  distinguish between green and red.
                 Mr Lee Again
• He has difficulty reading the text on many Web sites.
  When he first starting using the Web, it seemed to him
  the text and images on a lot of sites used poor color
  contrast, since they appeared to use similar shades of
  brown.
• He realized that many sites were using colors that were
  indistinguishable to him because of his red/green color
  blindness.
• In some cases the site instructions explained that
  discounted prices were indicated by red text, but all of
  the text looked brown to him. In other cases, the required
  fields on forms were indicated by red text, but again he
  could not tell which fields had red text.
                Mr Lee Continued
• Mr. Lee found that he prefered sites that used sufficient color
  contrast, and redundant information for color. The sites did this by
  including names of the colors of clothing as well as showing a
  sample of the color; and by placing an asterix (*) in front of the
  required fields in addition to indicated them by color.

• After additional experimentation, Mr. Lee discovered that on most
  newer sites the colors were controlled by style sheets and that he
  could turn these style sheets off with his browser or override them
  with his own style sheets. But on sites that did not use style sheets
  he couldn't override the colors.

• Eventually Mr. Lee bookmarked a series of online shopping sites
  where he could get reliable information on product colors, and not
  have to guess at which items were discounted.
  Reporter with repetitive stress
              injury

• Mr. Jones is a reporter who must submit
  his articles in HTML for publishing 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.
                  Mr Jones
• He uses a combination of speech recognition
  and an alternative keyboard to prepare his
  articles, but he doesn't use a mouse.
• It took him several months to become sufficiently
  accustomed to using speech recognition to be
  comfortable working for many hours at a time.
  There are some things he has not worked out
  yet, such as a sound card conflict that arises
  whenever he tries to use speech recognition on
  Web sites that have streaming audio.
             More Mr Jones
• He has not been able to use the same Web
  authoring software as his colleagues, because
  the application that his office chose for a
  standard is missing many of the keyboard
  equivalents that he needs in place of mouse-
  driven commands.
• To activate commands that do not have
  keyboard equivalents, he would have to use a
  mouse instead of speech recognition or typing,
  and this would re-damage his hands at this time.
           More Mr Jones
• He researched some of the newer
  versions of authoring tools and selected
  one with full keyboard support.
• Within a month, he discovered that several
  of his colleagues have switched to the new
  product as well, after they found that the
  full keyboard support was easier on their
  own hands.
                Mr Jones
• When browsing other Web sites to
  research some of his articles, Mr. Jones
  likes the access key feature that is
  implemented on some Web pages.
• It enables him to shortcut a long list of
  links that he would ordinarily have to tab
  through by voice, and instead go straight
  to the link he wants.
  Online student who is deaf
• Ms. Martinez is taking several distance
  learning courses in physics.
• She is deaf. She had little trouble with the
  curriculum until the university upgraded
  their on-line courseware to a multimedia
  approach, using an extensive collection of
  audio lectures.
                  MS Martinez
• For classroom-based lectures the university provided
  interpreters; however for Web-based instruction they
  initially did not realize that accessibility was an issue,
  then said they had no idea how to provide the material in
  accessible format.
• She was able to point out that the University was clearly
  covered by a policy requiring accessibility of online
  instructional material, and then to point to the Web
  Content Accessibility Guidelines 1.0 as a resource
  providing guidance on how to make Web sites, including
  those with multimedia, accessible.
               MS Martinez
• The University had the lectures transcribed and
  made this information available through their
  Web site along with audio versions of the
  lectures.
• For an introductory multimedia piece, the
  university used a SMIL-based multimedia format
  enabling synchronized captioning of audio and
  description of video. The school's information
  managers quickly found that it was much easier
  to comprehensively index the audio resources
  on the accessible area of the Web site, once
  these resources were captioned with text.
               Ms Martinez
• The professor for the course also set up a chat
  area on the Web site where students could
  exchange ideas about their coursework.
• Although she was the only deaf student in the
  class and only one other student knew any sign
  language, she quickly found that the Web-based
  chat format, and the opportunity to provide Web-
  based text comments on classmates' work,
  ensured that she could keep up with class
  progress.
    Accountant with blindness

• Ms. Laitinen is an accountant at an
  insurance company that uses Web-based
  formats over a corporate intranet. She is
  blind. She uses a screen reader to
  interpret what is displayed on the screen
  and generate a combination of speech
  output and refreshable braille output.
               Ms. Laitenen
• She uses the speech output, combined with
  tabbing through the navigation links on a page,
  for rapid scanning of a document, and has
  become accustomed to listening to speech
  output at a speed that her co-workers cannot
  understand at all.
• She uses refreshable braille output to check the
  exact wording of text, since braille enables her to
  read the language on a page more precisely.
                  Ms. Laitenen
• Much of the information on the Web documents used at
  her company is in tables, which can sometimes be
  difficult for non-visual users to read. However, since the
  tables on this company's documents are marked up
  clearly with column and row headers which her screen
  reader can access, she easily orients herself to the
  information in the tables.
• Her screen reader reads her the alternative text for any
  images on the site. Since the insurance codes she must
  frequently reference include a number of abbreviations
  and acronyms, she finds the expansions of abbreviations
  and acronyms the first time they appear on a page
  allows her to better catch the meaning of the short
  versions of these terms.
               Ms. Laitenen
• As one of the more senior members of the
  accounting staff, Ms. Laitenen must frequently
  help newer employees with their questions.
• She has recently upgraded to a browser that
  allows better synchronization of the screen
  display with audio and braille rendering of that
  information.
• This enables her to better help her colleagues,
  since the screen shows her colleagues the same
  part of the document that she is reading with
  speech or braille output.
Classroom student with dyslexia


• Ms. Olsen attends middle school, and
  particularly likes her literature class. She
  has attention deficit disorder with dyslexia,
  and the combination leads to substantial
  difficulty reading. However with recent
  accommodations to the curriculum she
  has become enthusiastic about this class.
                  Ms Olsen
• Her school recently started to use more online
  curricula to supplement class textbooks.
• She was initially worried about reading load,
  since she reads slowly.
• But recently she tried text to speech software,
  and found that she was able to read along
  visually with the text much more easily when she
  could hear certain sections of it read to her with
  the speech synthesis, instead of struggling over
  every word.
                  Ms Olsen
• Her classes recent area of focus is Hans
  Christian Andersen's writings, and she has to do
  some research about the author.
• When she goes onto the Web, she finds that
  some sites are much easier for her to use than
  others.
• Some of the pages have a lot of graphics, and
  those help her focus in quickly on sections she
  wants to read. In some cases, though, where the
  graphics are animated, it is very hard for her to
  focus, and so it helps to be able to freeze the
  animated graphics.
                 Ms Olsen
• One of the most important things for her has
  been the level of accessibility of the Web-based
  online library catalogues and the general search
  functions on the Web.
• Sometimes the search options are confusing for
  her.
• Her teacher has taught a number of different
  search strategies, and she finds that some sites
  provide options for a variety of searching
  strategies and she can more easily select
  searching options that work well for her.
   Retiree with several aging-related
conditions, managing personal finances
• Mr. Yunus uses the Web to manage some of his
  household services and finances. He has some
  central-field vision loss, hand tremor, and a little
  short-term memory loss.
• He uses a screen magnifier to help with his
  vision and his hand tremor; when the icons and
  links on Web pages are bigger, it's easier for him
  to select them, and so he finds it easier to use
  pages with style sheets.
               Mr Yunus
• When he first started using some of the
  financial pages, he found the scrolling
  stocktickers distracting, and they moved
  too fast for him to read.
• In addition, sometimes the pages would
  update before he had finished reading
  them.
                 Mr Yunus
• Therefore he tends to use Web sites that do not
  have a lot of movement in the text, and that do
  not auto-refresh. He also tended to "get stuck"
  on some pages, finding that he could not back
  up, on some sites where new browser windows
  would pop open without notifying him.
• Mr. Yunus has gradually found some sites that
  work well for him, and developed a customized
  profile at some banking, grocery, and clothing
  sites.
     Supermarket assistant with
        cognitive disability
• Mr. Sands has put groceries in bags for customers for
  the past year at a supermarket.
• He has Down syndrome, and has difficulty with abstract
  concepts, reading, and doing mathematical calculations.
• He usually buys his own groceries at this supermarket,
  but sometimes finds that there are so many product
  choices that he becomes confused, and he finds it
  difficult to keep track of how much he is spending. He
  has difficulty re-learning where his favorite products are
  each time the supermarket changes the layout of its
  products.
                  Mr Sands
• Recently, he visited an online grocery service
  from his computer at home. He explored the site
  the first few times with a friend.
• He found that he could use the Web site without
  much difficulty -- it had a lot of pictures, which
  were helpful in navigating around the site, and in
  recognizing his favorite brands.
• His friend showed him different search options that were
  available on the site, making it easier for him to find
  items. He can search by brand name or by pictures, but
  he mostly uses the option that lets him select from a list
  of products that he has ordered in the past. Once he
  decides what he wants to buy, he selects the item and
  puts it into his virtual shopping basket. The Web site
  gives him an updated total each time he adds an item,
  helping him make sure that he does not overspend his
  budget.
                     Mr Sands
• The marketing department of the online grocery wanted
  their Web site to have a high degree of usability in order
  to be competitive with other online stores.
• They used consistent design and consistent navigation
  options so that their customers could learn and
  remember their way around the Web site.
• They also used the clearest and simplest language
  appropriate for the site's content so that their customers
  could quickly understand the material.
               Mr Sands
• While these features made the site more
  usable for all of the online-grocery's
  customers, they made it possible for Mr.
  Sands to use the site.
• Mr. Sands now shops on the online
  grocery site a few times a month, and just
  buys a few fresh items each day at the
  supermarket where he works.
  Teenager with deaf-blindness,
     seeking entertainment

• Ms. Kaseem uses the Web to find new
  restaurants to go to with friends and classmates.
• She has low vision and is deaf.
• She uses a screen magnifier to enlarge the text
  on Web sites to a font size that she can read.
• When screen magnification is not sufficient, she
  also uses a screen reader to drive a refreshable
  braille display, which she reads slowly.
                Ms Kaseem
• At home, Ms. Kaseem browses local Web sites
  for new and different restaurants.
• She uses a personal style sheet with her
  browser, which makes all Web pages display
  according to her preferences.
• Her preferences include having background
  patterns turned off so that there is enough
  contrast for her when she uses screen
  magnification.
• This is especially helpful when she reads on-line
  sample menus of appealing restaurants.
               Ms Kaseem
• A multimedia virtual tour of local
  entertainment options was recently added
  to the Web site of the city in which Ms.
  Kaseem lives. The tour is captioned and
  described -- including text subtitles for the
  audio, and descriptions of the video --
  which allows her to access it using a
  combination of screen magnification and
  braille.
                Ms Kaseem
• The interface used for the virtual tour is
  accessible no matter what kind of assistive
  technology she is using -- screen magnification,
  her screen reader with refreshable braille, or her
  portable braille device.
• Ms. Kaseem forwards the Web site address to
  friends and asks if they are interested in going
  with her to some of the restaurants featured on
  the tour.
                   Ms Kaseem
• She also checks the public transportation sites to find
  local train or bus stops near the restaurants. The Web
  site for the bus schedule has frames without meaningful
  titles, and tables without clear column or row headers, so
  she often gets lost on the site when trying to find the
  information she needs.
• The Web site for the local train schedule, however, is
  easy to use because the frames on that Web site have
  meaningful titles, and the schedules, which are laid out
  as long tables with clear row and column headers that
  she uses to orient herself even when she has magnified
  the screen display.
              MS Kaseem
• Occasionally she also uses her portable
  braille device, with an infrared connection,
  to get additional information and directions
  at a publicly-available information kiosk in
  a shopping mall downtown;
• and a few times she has downloaded
  sample menus into her braille device so
  that she has them in an accessible format
  once she is in the restaurant.
   Different Disabilities that Can
      Affect Web Accessibility
• This section describes general kinds of
  disabilities that can affect access to the Web.
  There are as yet no universally accepted
  categorizations of disability, despite efforts
  towards that goal.
• Abilities can vary from person to person, and
  over time, for different people with the same type
  of disability.
• People can have combinations of different
  disabilities, and combinations of varying levels of
  severity.
                  Disability
• 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 of sensory,
  physical or cognitive functioning which can affect
  access to the Web.
• These may include injury-related and aging-
  related conditions, and can be temporary or
  chronic.
                 Aging
• The number and severity of limitations
  tend to increase as people age, and may
  include changes in vision, hearing,
  memory, or motor function.
• Aging-related conditions can be
  accommodated on the Web by the same
  accessibility solutions used to
  accommodate people with disabilities.
           Accommodations
• Sometimes different disabilities require similar
  accommodations.
• For instance, someone who is blind and
  someone who cannot use his or her hands both
  require full keyboard equivalents for mouse
  commands in browsers and authoring tools,
  since they both have difficulty using a mouse but
  can use assistive technologies to activate
  commands supported by a standard keyboard
  interface.
            Universal Design
• Many accessibility solutions described in this
  document contribute to "universal design" (also
  called "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.
           Some Disabilities


• Following is a list of some disabilities and
  their relation to accessibility issues on the
  Web.
  .
• visual disabilities
  – blindness
  – low vision
  – color blindness
• hearing impairments
  – deafness
  – hard of hearing
• physical disabilities
  – motor disabilities
• speech disabilities
   – speech disabilities
• cognitive and neurological disabilities
   – dyslexia and dyscalculia
   – attention deficit disorder
   – intellectual disabilities

   – memory impairments
   – mental health disabilities
   – seizure disorders
• multiple disabilities
• aging-related conditions
         Visual disabilities
• Blindness (scenario -- "accountant")
• 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.
       Text Based Browsers
• Some people who are blind use text-based
  browsers such as Lynx, or voice browsers,
  instead of a graphical user interface
  browser plus screen reader.
• They may use rapid navigation strategies
  such as tabbing through the headings or
  links on Web pages rather than reading
  every word on the page in sequence.
          Barriers(Blindness)
• Examples of barriers that people with blindness
  may encounter on the Web can include:
• images that do not have alternative 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 or "linearized" mode)
      More Barriers(Blindness)
• 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
• non-standard document formats that may be difficult for
  their screen reader to interpret
         Low vision (scenarios --
         "teenager" and "retiree")
• There are many types of low vision (also known as "partially sighted"
  in parts of Europe), 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 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 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(Low Vision)
• Web pages with absolute font sizes that do not change
  (enlarge or reduce) easily
• Web pages that, because of inconsistent layout, are
  difficult to navigate when enlarged, due to loss of
  surrounding context
• Web pages, or images on Web pages, that have poor
  contrast, and whose contrast cannot be easily changed
  through user override of author style sheets
• text presented as images, which prevents wrapping to
  the next line when enlarged
• also many of the barriers listed for blindness, above,
  depending on the type and extent of visual limitation
     Color blindness (scenario --
              "shopper")
• 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(Colour Blindness)
• 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 Impairments
• Deafness (scenario -- "online student")
• 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 a written language fluently, or
  speak clearly.
  To use the Web, many people who are deaf rely on
  captions for audio content. They may need to turn on the
  captions on an audio file as they browse a page;
  concentrate harder to read what is on a page; or rely on
  supplemental images to highlight context.
         Barriers Deaf People
• lack of captions or transcripts of audio on the
  Web, including webcasts

• lack of content-related images in pages full of
  text, which can slow comprehension for people
  whose first language may be a sign language
  instead of a written/spoken language
• lack of clear and simple language

• requirements for voice input on Web sites
              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 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 can include:
• lack of captions or transcripts for audio on the Web,
  including webcasts
        Physical disabilities
• Motor disabilities (scenario -- "reporter")
• Motor disabilities can include weakness,
  limitations of muscular control (such as
  involuntary movements, lack of coordination, or
  paralysis), limitations of sensation, joint
  problems, or missing limbs.
• Some physical disabilities can include pain that
  impedes movement. These conditions can affect
  the hands and arms as well as other parts of the
  body.
           Motor Difficulties
• To use the Web, people with motor disabilities
  affecting the hands or arms may use a
  specialized mouse;
• a keyboard with a layout of keys that matches
  their range of hand motion;
• a pointing device such as 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.
            Motor Difficulties
• They may activate commands by typing single
  keystrokes in sequence with a head pointer
  rather than typing simultaneous keystrokes
  ("chording") to activate commands.
• They may need more time when filling out
  interactive forms on Web sites if they have to
  concentrate or maneuver carefully to select each
  keystroke.
   Barriers (Motor Difficulties)
• time-limited response options on Web
  pages
• browsers and authoring tools that do not
  support keyboard alternatives for mouse
  commands
• forms that cannot be tabbed through in a
  logical order
• Speech disabilities
• 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 can include:
• Web sites that require voice-based interaction and have
  no alternative input mode
     Cognitive and neurological disabilities
  Visual and Auditory Perception (scenario --
                "classroom student")
• Individuals with visual and auditory perceptual
  disabilities, including dyslexia (sometimes called
  "learning disabilities" in Australia, Canada, the
  U.S., and some other countries) and dyscalculia
  may have difficulty processing language or
  numbers.
• They may have difficulty processing spoken
  language when heard ("auditory perceptual
  disabilities"). They may also have difficulty with
  spatial orientation.
   Visual and Auditory Perceptual
             Difficulties
• To use the Web, people with visual and auditory
  perceptual 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
• Barriers that people with visual and
  auditory perceptual disabilities may
  encounter on the Web can 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
     Attention deficit disorder (scenario --
             "classroom student")

• 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(Attention Deficit)
• distracting visual or audio elements that
  cannot easily be turned off
• lack of clear and consistent organization of
  Web sites
Intellectual disabilities (scenario
   -- "supermarket assistant")
• Individuals with impairments of intelligence
  (sometimes called "learning disabilities" in
  Europe; or "developmental disabilities" or
  previously "mental retardation" in the United
  States) may learn more slowly, or have difficulty
  understanding complex concepts.
• Down Syndrome is one among many different
  causes of intellectual disabilities.
                Web Use
• To use the Web, people with intellectual
  disabilities 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(intellectual)
• Barriers can include:
• use of unnecessarily complex language on
  Web sites
• lack of graphics on Web sites
• lack of clear or consistent organization of
  Web sites
Memory impairments (scenario --
          "retiree")
• Individuals with memory impairments may have
  problems with short-term memory, missing long-term
  memory, or may have some loss of ability to recall
  language.

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

  Barriers can include:
• lack of clear or consistent organization of Web sites
     Mental health disabilities
• Individuals with mental health 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 mental health disabilities
  may need to turn off distracting visual or audio elements,
  or to use screen magnifiers.
  Barriers can include:
• distracting visual or audio elements that cannot easily be
  turned off
• Web pages with absolute font sizes that do not enlarge
  easily
               Seizure disorders
• Some individuals with seizure disorders, including people with some
  types of epilepsy (including photo-sensitive epilepsy), 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 helps prevent
  triggering of seizures.


• Barriers can include:

• use of visual or audio frequencies that can trigger seizures
 Multiple Disabilities (scenario --
           "teenager")
• Combinations of disabilities may reduce a user's
  flexibility in using accessibility information.
• For instance, while someone who is blind can
  benefit from hearing an audio description of a
  Web-based video, and someone who is deaf
  can benefit from seeing the captions
  accompanying audio, someone who is both deaf
  and blind needs access to a text transcript of the
  description of the audio and video, which they
  could access on a refreshable braille display.
          Multiple Disabilities
• Similarly, someone who is deaf and has low
  vision might benefit from the captions on audio
  files, but only if the captions could be enlarged
  and the color contrast adjusted.
• Someone who cannot move his or her hands,
  and also cannot see the screen well, might use a
  combination of speech input and speech output,
  and might therefore need to rely on precise
  indicators of location and navigation options in a
  document.
      Aging-Related Conditions
        (scenario -- "retiree")
• Changes in people's functional ability due to aging can
  include changes in abilities or a combination of abilities
  including vision, hearing, dexterity and memory. Barriers
  can include any of the issues already mentioned above.
  Any one of these limitations can affect an individual's
  ability to access Web content. Together, these changes
  can become more complex to accommodate.
• 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.
       6. General References
• [ATAG10]
  – "Authoring Tool Accessibility Guidelines 1.0", J. Treviranus, C.
    McCathieNevile, I. Jacobs, and J. Richards, eds., 3 February
    2000. W3C Recommendation: http://www.w3.org/TR/2000/REC-
    ATAG10-20000203/.
• [WCAG-CURRIC]
  – "Curriculum for Web Content Accessibility Guidelines,"...
• [SMIL]
  – "Synchronized Multimedia Integration Language,"..
• [UAAG10]
  – "User Agent Accessibility Guidelines", J. Gunderson and I.
    Jacobs, eds., 28 July 2000. W3C Recommendation:
    http://www.w3.org/TR/2002/REC-UAAG10-20021217/.
               More References
• [WCAG10]
   – "Web Content Accessibility Guidelines 1.0", G. Vanderheiden,
     W. Chisholm, and I. Jacobs, eds., 5 May 1999. W3C
     Recommendation: http://www.w3.org/TR/1999/WAI-
     WEBCONTENT-19990505/.
• [WAI-Home]
   – "WAI Home Page", 1997-2000. http://www.w3.org/WAI/.
• [WAI-Resources]
   – "WAI Resources", 2000-2001.
     http://www.w3.org/WAI/Resources/.
• 7. Further Reading
•