Principle 4: Robustable Guidelines
WCAG Robust Success Criteria
Content must be robust enough that it can be interpreted reliably by a wide variety of user agents, like browsers and assistive technologies. This means that users must be able to access the content as technologies advance. Meeting this requirement helps maximize compatibility with current and future user agents, like screen readers. In particular, it enables assistive technologies to process the content reliably, and to present or to operate it in different ways. This includes non-standard (scripted) buttons, input fields, and other controls. To deliver a desirable user experience, there must be a separation between web page design and user content. The web page may not render as expected in all browsers, and will not perform as expected in differing screen readers. A design utilizing style sheets and Java Script widgets may improve the robustness. Note, the Accessibility Rich Internet Application (ARIA) code should only be used on a web page if the native HTML code cannot implement the desired effect. ARIA code will not have any effect on older browsers.
Guideline 4.1 Parsing
Maximize compatibility with current and future user agents, including assistive technologies. The intent of this Success Criterion is to ensure that user agents, like browsers and screen readers, can accurately interpret and parse content. If the content cannot be parsed into a data structure, then different user agents may present it differently or be completely unable to parse it. Some user agents use
repair techniques to render poorly coded content. In markup languages, errors in element and attribute syntax, and failure to provide properly nested start/end tags lead to errors that prevent user agents from parsing the content reliably. ensure that Assistive Technologies can gather information about, activate, and keep up to date on the status of user interface controls in the content.
When standard controls from accessible technologies are used, this process is straightforward. However, if custom controls are created, or interface elements are programmed (through scripts), to have a different role and/or function than usual, then additional measures need to be taken to ensure that the controls provide important information to assistive technologies and allow themselves to be controlled by assistive technologies. Also, it is important to make users aware of important changes in content that are not given focus, and to do so in a way that doesn’t unnecessarily interrupt their work. The scope of this Success Criterion is specific to changes in content that involve status messages.