Markup Validity

Accessibility Techniques for Markup Validity
Topic Technique WCAG AA Requirement
Unique Identifiers Unique IDs: IDs MUST be unique within a web page. Required
WCAG 4.1.1

Unique Names: The "accessible names" of elements, when provided, of block level elements (e.g. landmarks, tables, iframes, etc.) SHOULD be unique within a web page.

Note: The accessible name is determined by attributes or elements such as aria-label, aria-labelledby, alt, <caption>, etc. Refer to the Accessible Name and Description Computation for details.

best practice
One Attribute Instance: Elements MUST NOT contain more than one instance of the same attribute. Required
WCAG 4.1.1
Well Formed Closing Tags: Elements must not be missing closing tags.
DIV or P element must not be nested within a LABEL element.
Element must not contain duplicate attributes.
WCAG 4.1.1
Nesting and Relationships Parent-Child Relationships: Markup MUST adhere to required parent-child relationships of elements and attributes. Required
WCAG 4.1.1
ARIA relationships: ARIA relationships (e.g. parent-child, aria-owns, etc.) SHOULD adhere to WAI-ARIA Authoring Practices Required
WCAG 4.1.1
Deprecated Markup Deprecated Markup should not be used. best practice