When using headers in a document, you must make sure that your document follows the correct, accessibly structure. Make sure your headers follow in order (i.e. <h1> then <h2> then <h3> and so on)
To fix the structure:
- Find the list in the Accessibility Checker panel by right-clicking (Windows) or Ctrl-clicking (Mac OS) the failed element and choosing Show in Tags Panel.
- Create elements, change the types of elements, or rearrange existing elements by dragging them.
Be sure that your headers follow he right structure. Header levels can only go up or down ONE level at a time, and there can only be a single level one header on a page at a time.