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Accessibility - A Primer (Dutch PHP Conference 2009)
1. Web Accessibility // A Primer
Dutch PHP Conference
12.06.2009
Christian Wenz, Arrabiata Solutions GmbH
Mail: christian.wenz@arrabiata.de
WWW: http://www.arrabiata.de/
Blog: http://www.hauser-wenz.de/blog/
Twitter: @chwenz
2. Accessibility // Definition
• Making a website usable for all kinds of handicaps –
including older and younger people
• Handicaps may include eyesight, hearing,
understanding, using the computer
• There are several guidelines on accessibility. They are
useful, but often heavily debated.
– The user experience matters
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3. Accessibility // Rules
• In order to make accessibility manageable, there are
several rulesets and guidelines
– By W3C
– By governments (e.g. the USA´s Section 508, the
Ministerraad´s Besluit Kwaliteit
Rijksoverheidswebsites, German BITV, …)
• Many national regulations are based on the W3C rules
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4. W3C // Accessibility
• Web Accessibility Initiative (WAI)
– Homepage: http://www.w3.org/WAI/
• Web Content Accessibility Guidelines (WCAG)
– Version 1.0 from May 1999
– 14 guidelines, 65 checkpoints
– Three categories
• Priority 1: MUST
• Priority 2: SHOULD
• Priority 3: MAY
– http://www.w3.org/TR/WCAG10/
– Complete checklist: http://www.w3.org/TR/WCAG10/full-checklist.html
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5. WCAG // Version 1.0
• 1. Provide equivalent alternatives • 8. Ensure direct accessibility
to auditory and visual content. of embedded user interfaces.
• 2. Don't rely on color alone. • 9. Design for device-
• 3. Use markup and style sheets independence.
and do so properly. • 10. Use interim solutions.
• 4. Clarify natural language usage • 11. Use W3C technologies and
• 5. Create tables that transform guidelines.
gracefully. • 12. Provide context and
• 6. Ensure that pages featuring orientation information.
new technologies transform • 13. Provide clear navigation
gracefully. mechanisms.
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• 7. Ensure user control of time- • 14. Ensure that documents are
sensitive content changes. clear and simple.
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6. WCAG // Version 2.0
• Version 2.0 from December 2008
• http://www.w3.org/TR/WCAG20/
• Four principles, twelve guidelines
• Several success criteria per guideline (61 in total), with specific
"how to meet" and "understanding" information
• Sufficient techniques vs. advisory techniques
• Documented common failures
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8. WCAG 2.0 // Perceivable
• 1.1 Text Alternatives: Provide text alternatives for any non-text
content so that it can be changed into other forms people need, such
as large print, braille, speech, symbols or simpler language.
– 1.1.1: Non-text content but controls, time-based media, test,
sensory, CAPTCHAs, decoration. (Level A)
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9. WCAG 2.0 // Perceivable
• 1.2 Time-Based Media: Provide alternatives for time-based media.
– 1.2.1: Prerecorded Audio-only and video-only (Level A)
– 1.2.2: Prerecorded Captions (Level A)
– 1.2.3: Prerecorded Audio Description or Media Alternative (Level
A)
– Level AA: Live captions, …
– Level AAA: Prerecorded sign language, …
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10. WCAG 2.0 // Perceivable
• 1.3 Adaptable: Create content that can be presented in different
ways (for example simpler layout) without losing information or
structure.
– 1.3.1: Info and relationships (Level A)
– 1.3.2: Meaningful sequence (Level A)
– 1.3.3: Sensory characteristics (Level A)
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11. WCAG 2.0 // Perceivable
• 1.4 Distinguishable: Make it easier for users to see and hear
content including seperating foreground from background.
– 1.4.1: Use of color (Level A)
– 1.4.2: Audio control (Level A)
– Level AA: Contrast, resize text, …
– Level AAA: Enhanced contrast, low/no background audio, …
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12. WCAG 2.0 // Operable
• 2.1 Keyboard Accessible: Make all functionality available from a
keyboard.
– 2.1.1: Keyboard (Level A)
– 2.1.2: No keyboard trap (Level A)
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13. WCAG 2.0 // Operable
• 2.2 Enough Time: Provide users enough time to read and use
content.
– 2.2.1: Timing adjustable (Level A)
– 2.2.2: Pause, stop, hide (Level A)
– Level AAA: Interruprions, re-authenticating, …
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14. WCAG 2.0 // Operable
• 2.3 Seizures: Do not design content in a way that is known to cause
seizures.
– 2.3.1: Three flashes or below threshold (Level A)
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15. WCAG 2.0 // Operable
• 2.4 Navigable: Provide ways to help users navigate, find content,
and determine where they are.
– 2.4.1: Bypass blocks (Level A)
– 2.4.2: Page titled (Level A)
– 2.4.3: Focus order (Level A)
– 2.4.4: Link purpose in context (Level A)
– Level AA: Headings and labels, focus visible, …
– Level AAA: Location, link purpose (link only), section headings
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16. WCAG 2.0 // Understandable
• 3.1 Readable: Make text content readable and understandable.
– 3.1.1: Language of page (Level A)
– Level AA: Language of part
– Level AAA: Unusual words, abbreviations, pronounciation, …
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17. WCAG 2.0 // Understandable
• 3.2 Predictable: Make web pages appear and operate in predictable
ways.
– 3.2.1: On focus (Level A)
– 3.2.2: On input (Level A)
– Level AA: Consistent navigation, …
– Level AAA: Change on request
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18. WCAG 2.0 // Understandable
• 3.3 Input Assistance: Help users avoid and correct mistakes.
– 3.3.1: Error identification (Level A)
– 3.3.2: Label and instructions (Level A)
– Level AA: Error suggestion, error prevention (reverse, check,
confirm)
– Level AAA: Context-sensitive help, full error prevention
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19. WCAG 2.0 // Robust
• 4.1 Compatible: Maximize compatibility with current and future user
agents, including assistive technologies.
– 4.1.1: Parsing (Level A)
– 4.1.2: Name, role, value (Level A)
– Level AA: Language of part
– Level AAA: Unusual words, abbreviations, pronounciation, …
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20. Accessibility // Resources
• WCAG 1.0: http://www.w3.org/TR/WCAG10/
• WCAG 2.0: http://www.w3.org/TR/WCAG20/
• How to Meet WCAG 2.0: http://www.w3.org/WAI/WCAG20/quickref/
• Understanding WCAG 2.0:
http://www.w3.org/TR/UNDERSTANDING-WCAG20/
• Techniques for WCAG 2.0: http://www.w3.org/TR/WCAG20-TECHS/
• Migrating from WCAG 1.0 to WCAG 2.0:
http://wipa.org.au/papers/wcag-migration.htm
• http://webrichtlijnen.nl/
• http://fronteers.nl/
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