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Understanding Web Accessibility

November 12, 2015.

Voir la carte WCAG 2.0

« Web accessibility means making the Web accessible to people with disabilities. More specifically, it means that the disabled can perceive, understand, navigate and interact with the Web, and contribute to it. Web accessibility also benefits other users, such as older people with diminished faculties due to the normal ageing process.»
Source: Web Accessibility Initiave (W3C)

Accessibility is also an issue for anyone experiencing problems or limitations accessing Internet content, such as:

  • People with a slow internet connection
    People with little to no experience with the Web
    People using devices other than a computer to surf the Web (mobile phones, tablets, etc.)
    People using obsolete browsers or computers (ex: an old version of a browser)

In Canada, Web site accessibility standards became law on August 1st, 2011, and were updated on March 31, 2013. The Act requires all institutions contemplated in parts 1, 1.1 and 2 of the Financial Administration Act to comply with A and AA priority Web access rules.

The WC3 has released two checklist-style guidelines to verify the accessibility of Web content:

Guideline WCAG 1.0 (1999) deals mainly with HTML content. Guideline WCAG 2.0 (2006) deals mainly with technology. Each control point has been assigned a priority rating.

Principles of Accessibility

Accessibility standards are based on 4 basic principles:

1. Perceivability

  • Web site interfaces must be compatible with terminals used by the disabled with no loss of content.
  • Equivalent alternatives must be provided for visual and audio content (static or animated images, audio and visual content, sound, etc.)
  • Font size must be increasable by 200% with no loss of content and no sideways scrolling

2. Usability

  • Keyboard: All Web site functions must be keyboard enabled, being accessed with the Tab key and activated with the Enter key. Functions being accessed must be visually distinctive.
  • Visual contrast: The contrast ratio between text and background colours must be at least 4.5:1
  • Navigation: Navigation must be facilitated through visual cues, such as page titles, links for skipping blocks, and visually distinctive active functions.

3. Intelligibility

  • Web site content must be easy to read and to understand.
  • Structure: Pages must be structured using header markers h1 to h6.
  • Abbreviations: A system must be provided to decipher abbreviations.

4 - Robustness

  • Compatibility: Site must be compatible with diverse browsers and screen readers.
  • Compliance: Site must comply with W3C rules.
  • Name, role, value: All user interface components must have a name, role or value (ex: the various parts of forms).

Web Site Accessibility Assessment Toolkit

Though many different tools can provide an assessment of Web site accessibility, none of them provide the complete package. You still have to perform a manual check.