Markup Validity
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Topic
Technique
WCAG AA Requirement
Unique Identifiers
Unique IDs: IDs MUST be unique within a web page.
Required
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.
best practice
One Attribute Instance: Elements MUST NOT contain more than one instance of the same attribute.
Required
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.
Required
Nesting and Relationships
Parent-Child Relationships: Markup MUST adhere to required parent-child relationships of elements and attributes.
Required
ARIA relationships: ARIA relationships (e.g. parent-child, aria-owns, etc.) SHOULD adhere to
Required
Deprecated Markup
Deprecated Markup should not be used.
best practice