Annotations, as the name implies^⌖3, allow you to associate annotations with content in your document. Annotations are non-local (they’re associated by ID/IDREF not containment) and the linking markup is bi-directional^⌖4. The same annotation can^⌖2 be used more than once^⌖2.

Annotations can be rendered with or without JavaScript support. With JavaScript, the annotations are popups. Without JavaScript, they’re presented at the bottom of the page, similar to footnotes, but styled somewhat differently. In paged media, annotations are rendered as footnotes and their titles are ignored.