From W3C Wiki
Differences between the W3C HTML 5.1 specification and the WHATWG LS
The W3C HTML 5.1 specification:
- Requires the main element be mapped to the ARIA role 'main' or equivalent in accessibility APIs. Rationale: Improve interoperability.
- Restricts the author use of the main element to one per document. Rationale: Improve utility for users.
- Encourages user agents to provide keyboard navigation for the main element. Rationale: Improve utility for users.
- Defines the main element as representing the main content of a document. Rationale: Matches markup patterns used by authors to identify the main content area of a document.
- Defines the body element as representing the content of the document. Rationale: The main element represents the main content of a document.
- Provides clarification for authors on the use of list markup in the nav element. Rationale: Improve author advice and user experience.
- Advises authors to use headings of the appropriate rank for a section's nesting level. Rationale: backwards compatibility and improve user experience.
- The hgroup element is obsolete. Rationale: Lack of implementations, lack of use cases, promoted markup anti-pattern.
- Provides author advice on marking up Subheadings, subtitles, alternative titles and taglines. Rationale: HTML does not have a dedicated feature for marking up such semantics, so provides author advice on how to do it using current features.
- Requires that the header and footer elements be mapped to ARIA landmark roles dependent on their ancestor elements. Rationale: Match landmark definitions and interoperable implementations.
- Restricts the elements that authors can use ARIA role=presentation on. Rationale: Use of role=presentation on interactive elements has no use cases and can cause issues for AT users.
- Provides normative text and an example for link type license which advises authors to state in text the scope of document license if it does not apply to the whole document. Rationale: Use of CSS styles are inadequate for conveying the scope of a license.
- Includes a detailed text explanation of the th element example and related image. Rationale: The example is complex, and extra detail is required to explain information conveyed visually.
- Discourages use of the title attribute in cases where its content should be available to all/any user
- makes the use of the title attribute for providing image captions non conforming, as in 18 year history it has not been implemented in an interoperable, input device independent manner. Instead it promotes the use of the figure and figcaption elements for the provision of image captions. The figcaption element content is by default available to all and it conveys a caption role to assistive technology. Rationale: improves accessibility and usability.