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Introduction To WCAG 2.0

The Web Content Accessibilitylines (WCAG) 2.0 are a set of guidelines maintained by the World Wide Web Consortium (W3C) for making content more accessible to people with disabilities

Web content is implemented through web content technologies and accessed using user agents (with or without assistive technologies).


HTML is a type of web content technology.

Web browsers are a type of user agent.

Screen readers are a type of assistive technology.

To ensure content is accessible to the widest possible audience, Government of Canada web pages must meet all five WCAG 2.0 conformance requirements under the Standard on Web Accessibility. Web pages satisfy conformance requirements by using the thirty-eight (38) success criteria listed at the A and AA levels of WCAG 2.0.

Applicable success criteria

Success criteria are general statements, independent of technology, that need to be satisfied for content to claim conformance to WCAG 2.0.

Depending on the type of content on a web page, individual success criterion may apply to all, some, or none of the content.

For assistance determining what content is applicable to a success criterion, consult the WCAG 2.0 Success Criteria Applicability.


Success Criterion 1.2.2: Captions (Prerecorded) applies to captioning of video (with audio) and applies only to video (with audio) elements on a web page.

Success Criterion 1.4.4: Resize Text applies to the ability to resize text on a web page and applies to all text on a web page.

Satisfying success criteria

Success criteria are satisfied by:

  • Avoiding all common failures; and

  • Applying applicable sufficient techniques specific to the technologies used on the web page.

The step by step process to satisfy a success criterion follows:

  1. For each success criterion, identify the applicable items of content on the web page.

  2. For each occurrence of an applicable item of content:

    1. Identify the web content technology used to implement the item.

    2. If present in the success criterion's list of sufficient techniques, identify the applicable situation.

    3. Ensure at least one sufficient technique from the success criterion (specific to the situation and web content technology used) is being satisfied. General sufficient techniques can be used by all web content technologies.

    4. Ensure the item avoids all common failures.


Scenario: A HTML web page contains only headings and paragraphs. Headings are short text phrases which identify the section of content that immediately follows it.

  1. For Success Criterion 1.3.1 Info and Relationships, any content conveying the meaning of a "heading" is applicable.

  2. For each "heading":

    1. HTML is the web content technology used to implement the item.

    2. Situation A applies as HTML provides semantic structure to make information and relationships conveyed through presentation programmatically determinable.

    3. Technique H42, which is an HTML technique under Situation A, is satisfied by marking up the "heading" with <h1>, <h2>, etc.

    4. Failures F2 and F43 are avoided by ensuring all items that look like "headings" and only those items that are actually "headings" are marked up using Technique H42.

When a success criterion cannot be satisfied

When an item of content cannot satisfy all applicable success criteria using a desired web content technology, an alternate version of the item in another web content technology that does satisfy all applicable success criteria must be provided.

The original version does not need to be removed as long as it does not interfere with a user's ability to easily locate and access the alternate version and use the web page. The original version must also not present any additional information and/or functionality which is not found in the alternate version.

Note: An item of content that does not satisfy all applicable success criteria will not be fully supported by assistive technologies and accessibility features in user agents such as web browsers. This means that it is not possible for a user to access it in an accessibility-supported way.


Scenario: A Java Applet

No success criterion can be satisfied because there are no sufficient techniques defined for Java Applet technology.

Solution: The applet's content would need to be provided in an alternate version. If the applet interferes with the usage of the web page, such as trapping keyboard functionality, it must be removed.

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