All web pages must have complete start and end tags, be nested according to their specifications, not contain duplicate attributes, and IDs must be unique. To ensure ADA compliance, use our free html validation plugin to identify and correct validation errors in your pages. The pro extension may be used to correct many of HTML validation issues automatically.
Reference: opens in a new windowWCAG 2.1 (Level A) – 4.1.1
Additional Resources From W3.org
- G134: Validating Web pages
- G192: Fully conforming to specifications
- H88: Using HTML according to spec
- H74: Ensuring that opening and closing tags are used according to specification
- H93: Ensuring that id attributes are unique on a Web page
- H94: Ensuring that elements do not contain duplicate attributes
- H75: Ensuring that Web pages are well-formed
- F70: Failure of Success Criterion 4.1.1 due to incorrect use of start and end tags or attribute markup
- F77: Failure of Success Criterion 4.1.1 due to duplicate values of type ID
