Footnotes and endnotes have proven an impediment to the reading experience because they interrup the narrative flow. When footnotes are placed immediately following the paragraph that references them, readers had to manually navigate past them each time, as they are typically indistinguishable from text content. Even endnotes, grouped at the end of the section, require the user to jump past them.
The HTML5 structural elements, together with the
epub:type attribute, provide a means of
alleviating this problem, by clearly marking individual footnotes and endnotes, and sections of them. Not
only does this allow accessible reading systems to ignore the notes except when followed from their
referents, but it allows any reading system to handle them more intelligently (e.g., as pop-ups).
Notes placed within the primary narrative should be tagged using the HTML5
aside element (see
Example 1). This usage ensures that even if the EPUB semantic is not
recognized, the notes will still be treated as secondary content due the nature of the HTML5
The type of note must be identified using the
epub:type attribute. The EPUB 3 Structural Semantics Vocabulary defines the
following note types:
footnote— a note that would normally be placed at the bottom of a print or electronic page
endnote— a note that would normally be placed at the end of a section or publication
Notes that are grouped at the end of a section do not need to be individually tagged as
aside, but should be grouped in a
section carrying the appropriate
endnotes semantic (see Example 2). Lists are an effective means of representing groups of notes in
these sections, as they allow readers to move through them more effectively (e.g., each list item number
will typically correspond sequentially to the contained note number, and readers should have the ability
to jump through more than one list item at a time when there are many notes).
Notes in Tables
If notes occur in a table, avoid placing them in a
tfoot element, as it is intended for
summaries of the columns. Footnotes can follow the table or can be grouped together with the table inside
figure. See the Tables section for an example.
Note references must be tagged using the HTML5
a element with an
attribute designating the property
Do not use the
sup element to superscript note references, as it is redundant presentational
tagging. The CSS
vertical-align property can be set to superscript the
elements. (See Example 3 below.)
Although not specifically required to be accessible, it is good practice to back-link groups of notes to their referent locations in the text (see Example 4). If a reader is surveying your notes, this will allow them to quickly find the text the note refers to.