Transcript Web Content Accessibility Guidelines

Web
Accessibility
Bernie D. Davenport & A. Craig Dixon
September 26, 2007
Web Accessibility Defined
Web accessibility refers to making web resources
utile for all users, regardless of disability.
The cardinal rule of web accessibility is that all
users must be able to use the parts of the site
that are essential to its message and function.
Making web sites accessible requires some
knowledge of the various kinds of assistive
technologies used by people with disabilities to
access the Web.
Making web sites accessible often has the
beneficial side effect of adding ease of use or
additional functionality for users without
disabilities.
Types of Disabilities
Web Accessibility in Mind (WebAIM) defines
five types of disabilities of which web
designers should be cognizant.
Visual
Auditory
Motor
Cognitive
Seizure
Visual Disabilities
Visual disabilities include blindness, low vision,
and colorblindness.
Low vision users may utilize screen magnifiers or
high contrast color schemes in order to see the
information on the page more clearly.
Blind users may utilize screen reader technologies
that audibly read the contents of the page to the
user.
Because some users may be colorblind, page
designers should never use color alone to convey
a piece of information.
Auditory Disabilities
Auditory disabilities include deafness and
hardness of hearing.
Audio content that is critical to the message
or function of the web resource should be
captioned or transcribed.
Audio content should be clear and free from
background noise so it can be easily
perceived by users who are hard of hearing.
Motor Disabilities
Motor disabilities include limited range of motion,
slowness of motor response, and lack of fine motor
control. These disabilities may be the result of bone or
neuromuscular diseases, broken bones, or amputation.
Users with motor disabilities often find using the
keyboard preferable to using the mouse. Care should
be taken to ensure that all page functions can be
performed independent of the user’s input device.
Time-sensitive tasks should also be avoided. If timesensitive tasks are necessary, the user must easily be
able to request more time to complete the task.
Cognitive Disabilities
Cognitive disabilities include learning disabilities, high
susceptibility to distraction, an inability to process large
amounts of information, and short-term memory loss.
Many of the design principles for dealing with cognitive
disabilities overlap with general principles of good web design.
For example, writing to the lowest reading level appropriate for
the intended audience.
Because a user’s reading level often affects the speed at which
they can read and process information, scrolling or marquee text
should be avoided. If scrolling or marquee text is used,
mechanisms for controlling its speed should be utilized.
Often, graphics, diagrams, tables, etc. are useful in addressing
cognitive disabilities. Care must be taken to make these visual
aides as simple and understandable as practical, and the
designer must account for visually-impaired users when
including these elements in the page’s design.
Seizure Disabilities
Some people are subject to photoepileptic
seizures when viewing content that flashes,
strobes, flickers, or blinks at a certain frequency.
Content that blinks or flashes can also be
distracting, making it a potential problem for
those with cognitive disabilities as well. Because
of this, blinking or flashing content should be
avoided.
If the content cannot be avoided, the user must
be warned in advance about the presence of
blinking or flashing content and possibility of
triggering a seizure.
Accessibility Goals
WebAIM further defines four accessibility
goals for web content. These are referred to
by the acronym POUR.
Perceivable
Operable
Understandable
Robust
Perceivability
Perceivability refers to the ability of a user to
access critical content via one of the senses that
he or she has sufficient use of.
For blind users, this could be audio perception.
For deaf users, this could be visual perception.
For deaf-blind users, this could be tactile perception
via a Braille output device.
The most efficient way to achieve accessibility is
to ensure that content is transformable from one
form to another.
Text is the most transformable medium.
Content must be separated from presentation.
Operability
Operability refers to the ability of a user to locate
and interact with the critical content of the page.
Some disabilities render users unable to use a
mouse. Others make it preferable for the user to
use a keyboard. Keyboard accessibility is one of
the most crucial concepts in web accessibility.
Efficient navigation is also a part of operability.
Users should be able to skip parts of the page that
are not relevant to them.
In this way, site indices and search functions are
components of good operability.
Proper heading structures and good organization of
information and links is also important.
Understandability
Understandability refers to the user being able to
process the content and respond accordingly.
Use of appropriate reading level and use of
supplemental charts, graphics, etc. are important
aspects of understandability.
Understandability is also important in complex, multistep processes like filling out a form or placing an
order.
Consistent design can be a major boost to
understandability. Users quickly learn where to find
the elements of your site (navigation controls,
branding information, etc.) and are able to focus their
attention on the content itself.
Robustness
Robustness refers to the ability of the user to get a
consistent experience from the web resource
regardless of the technology used to access it.
Designers should account for differences in operating
systems, browsers, browser versions, and settings and
ensure that the web resource behaves the same way in
as many configurations as possible.
Designers should only require users to download
additional resources such as plug-ins when expressing
the content in another way is not practical.
The user’s connection speed plays a role in robustness
as well. Tasks that require large downloads may be
considered inaccessible for users that do not have
broadband Internet connections.
World Wide Web
Consortium (WC3)
Created in October 1994
Mission – “…to lead the World Wide Web to its full
potential by developing common protocols that promote
its evolution and ensure its interoperability.”
450 member organizations worldwide
Developed the Web Accessibility Initiative (WAI)
team
To promote a “high degree of usability for people with
disabilities.”
Developed Web Content Accessibility Guidelines
W3C Guidelines
Provides guidance on accessibility of Web sites
Contain 14 Guidelines for accessibility design
Provides Checkpoints for each Guideline
Makes pages more accessible to all users
Priorities and
Conformance Levels
Priorities are assigned to each Checkpoint
Priority 1 = developer must satisfy
Priority 2 = developer should satisfy
Priority 3 = developer may satisfy
Conformance Levels
Single-A = Priority 1 accessible
Double-A = Priority 1 & 2 accessible
Triple-A = Priority 1,2, & 3 accessible
WC3 Guidelines
Why?
To remove barriers from Web sites that
prevent people with disabilities from
accessing Web based information
To remove barriers in the “user agents”
Browsers
Multimedia players
Assistive Technologies
W3C Guidelines
Common Web Page Problems
Images without
alternative text
Image Maps or Hotspots
without alternative text
Misleading use of
structural elements such
as tables
Uncaptioned Audio
Un-described Video
Lack of alternative
information for users
who cannot access
frames or scripts
Tables that are difficult
to decipher when
linearized
Poor color contrasts and
color choices
W3C Guidelines
The following section provides
information concerning:
The 14 W3C Guidelines
The Related Checkpoints
Priority 1 P1 – Required by Jan 1, 2004
Priority 2 P2 – Should Incorporate
Priority 3 P3 – May Incorporate
W3C Guidelines
Guideline 1 of 14
Provide equivalent
alternatives to auditory
and visual content
1.1 P1 – Provide a text equivalent for
every non-text element.
1.2 P1 – Provide redundant text links
for each active region of a server-side
image map.
1.3 P1 – Provide an auditory description
of the important information of a visual
track.
1.4 P1 – Synchronize alternatives of a
visual track with the presentation.
1.5 P3 – Provide redundant text links
for each active region of a client-side
image map.
W3C Guidelines
Guideline 2 of 14
Don’t rely on Color
alone
2.1 P1 – All information conveyed with
color must also be available without
color.
2.2 P2, P3 – All foreground and
background color combinations must
provide sufficient contrast when viewed
on a black and white screen.
W3C Guidelines
Guideline 3 of 14
Use markup and style
sheets and do so
properly
3.1 P2 – Use markup rather than
images to convey information.
3.2 P2 – Validate to published formal
grammars.
3.3 P2 – Use style sheets to control
layout and presentation
3.4 P2 – Use relative rather than
absolute units.
3.5 P2 – Use Header elements to
convey document structure.
3.6 P2 – Mark up lists and list items
properly.
3.7 P2 –Mark up quotations.
W3C Guidelines
Guideline 4 of 14
Clarify natural language
used
4.1 P1 – Clearly identify changes in the
documents natural language.
4.2 P3 – Specify the expansion of each
abbreviation or acronym in a document
where it first occurs.
4.3 P3 – Identify the primary natural
language of a document.
W3C Guidelines
Guideline 5 of 14
Create tables that
transform gracefully
5.1 P1 – Identify row and column
headers for data tables.
5.2 P1 – Use mark up to associate data
cells and header cells.
5.3 P2 – Do not use table for layout
unless they make sense when
linearized.
5.4 P2 – If a table is used for layout, do
not use any structural markup for the
purpose of visual formatting.
5.5 P3 – Provide summaries for tables.
5.6 P3 – Provide abbreviations for
header labels.
W3C Guidelines
Guideline 6 of 14
Ensure that pages
featuring new
technologies transform
gracefully
6.1 P1 – Organize documents so that
they may be read without style sheets.
6.2 P1 – Equivalents for dynamic
content must be updated whenever the
dynamic content changes.
6.3 P1 – Ensure that pages are usable
when scripts, applets, etc are turned off
or not supported.
6.4 P2 – Ensure that event handlers are
input device independent.
6.5 P2 – Ensure that dynamic content is
accessible or provide an alternative.
W3C Guidelines
Guideline 7 of 14
Ensure user control of
time-sensitive content
changes
7.1 P1 – Avoid causing the screen to
flicker.
7.2 P2 – Avoid causing the content to
blink.
7.3 P2 – Avoid movement in pages.
7.4 P2 – Do not create periodically
refreshing pages.
7.5 P2 – Do not use mark up to redirect
pages automatically.
W3C Guidelines
Guideline 8 of 14
Ensure direct
accessibility of
embedded user
interfaces
8.1 P1, P2 – Make programmatic
elements such as scripts and applets
directly accessible or compatible with
assistive technologies.
W3C Guidelines
Guideline 9 of 14
Design for deviceindependence
9.1 P1 – Provide client-side image maps
instead of server-side image maps.
9.2 P2 – Ensure that any element that
has its own interface can be operated in
a device independent manner.
9.3 P2 – Specify logical event handlers
(on mouse over, on click, etc).
9.4 P3 – Create a logical tab order
through links, form controls and
objects.
9.5 P3 – Provide keyboard shortcuts to
important links.
W3C Guidelines
Guideline 10 of 14
Use interim solutions
(so that older browsers
and assistive
technologies will
operate correctly)
10.1 P2 – Do not cause pop-ups, new
windows, or change in current window
to occur without informing the user.
10.2 P2 – Ensure explicit associations
between labels and form controls.
10.3 P3 – Provide a linear text
alternative for tables that layout text in
parallel, word-wrapped columns.
10.4 P3 – Place holding characters in
edit boxes and text areas.
10.5 P3 – Include non-link printable
characters, (surrounded by spaces)
between adjacent links.
W3C Guidelines
Guideline 11 of 14
Use W3C technologies
and guidelines
11.1 P2 – Use W3C technologies when
they are available and appropriate for a
task (HTML 4.0).
11.2 P2 – Avoid depreciated features of
W3C technologies.
11.3 P3 – Provide information so that
users may receive documents according
to their preference.
11.4 P1 – If after best efforts, you
cannot create an accessible page,
provide a link to an alternative page.
W3C Guidelines
Guideline 12 of 14
Provide context and
orientation information
(to help users
understand complex
pages or elements)
12.1 P1 – Title each frame to facilitate
frame identification and navigation.
12.2 P2 – Describe the purpose of
frames and how they relate to each
other.
12.3 P2 – Divide large blocks of
information into more manageable
groups.
12.4 P2 – Associate labels explicitly
with their controls in a form.
W3C Guidelines
Guideline 13 of 14
Provide clear navigation
mechanisms
13.1 P2 – Clearly identify the target of
each link.
13.2 P2 – Provide metadata to pages
and sites.
13.3 P2 – Provide information about the
general layout of a site.
13.4 P2 – Use navigation mechanisms
in a consistent manner.
13.5 P3 – Provide navigation bars to
provide access to the navigation
mechanism.
More!
W3C Guidelines
Guideline 13 of 14
Provide clear navigation
mechanisms
13.6 P3 – Group related links and
provide a method to bypass the group.
13.7 P3 – If a search is provided,
enable different types of searches.
13.8 P3 – Place distinguishing
information at the beginning of
headings, paragraphs, lists, etc.
13.9 P3 – Provide information about
document collections (documents
comprising multiple pages).
13.10 P3 – Provide a means to skip
over multi-line ASCII art.
W3C Guidelines
Guideline 14 of 14
Ensure that documents
are clear and simple
14.1 P1 – Use the clearest and simplest
language appropriate for the site’s
content.
14.2 P3 – Supplement text with graphic
or auditory presentations where they
will facilitate the comprehension of the
page.
14.3 P3 – Create a style of presentation
that is consistent across pages.
WCAG 2.0 DRAFT
Applies to a wider range of current, future,
and non-W3C Web technologies
Requirements are more testable
Techniques are more comprehensive
Based upon Principles vs. Checkpoints
Although more comprehensive, most Web
sites that meet current WCAG 1.0 guidelines
should be able to pass the majority of WCAG
2.0 principle requirements
What is KCTCS doing
about web accessibility?
The Web Services Peer Team was formed last year to
develop standards regarding web properties. Part of
that charge includes drafting accessibility standards.
The Peer Team is consulting with KCTCS legal to
determine the minimum level of compliance required
by law.
From there, the Content and Accessibility sub-team
will make further recommendations regarding
compliance.
Your input is welcome!
Web Accessibility
Resources
http://www.section508.gov/
http://www.webaim.org/
http://www.w3.org/TR/WAI-WEBCONTENT/