Level A
In content implemented using markup languages, elements have complete start and end tags, elements are nested according to their specifications, elements do not contain duplicate attributes, and any IDs are unique, except where the specifications allow these features.>
Explanation
The code of the page must not cause browser or assistive technology conflicts. This ensures that content and functionality is presented in a way that works reliably across all supported browsers and assistive technologies.
Roles
- Development
- QA
Requirements
- all elements have the required opening and closing tags;
- All elements are nested properly according to their specification;
- Attributes are not duplicated on the same element;
- The values for
idattributes are unique to the currently exposed DOM.
Common mistakes
- An element requires both opening and closing tags, but the closing tag is missing;
- An interactive element like a link has been nested inside another interactive element like a button;
- An element has two instances of the same attribute;
- There are multiple
idattributes in the exposed DOM, and one or more share the same value.