Identifying notes and placing them at logical breaks in the text minimizes their impact on the reading of the primary text.
Footnotes and endnotes have proven an impediment to the reading experience because they interrupt the narrative flow. When footnotes are placed immediately following the paragraph that references them, users 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
role 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 user agents to ignore the notes except when followed from their
referents, but it allows any user agent 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 their semantics are not
recognized, the notes will still be treated as secondary content due the nature of the HTML5
Notes that are grouped at the end of a section do not need to be individually tagged as
aside, but should be grouped using the appropriate footnotes or endnotes semantic (see Example 2). Lists are an effective means of representing groups of notes in
these sections, as they allow users to move through them more effectively (e.g., each list item number
will typically correspond sequentially to the contained note number, and users 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 to ensure users do not
have to visually locate the corresponding note.
sup element may be used to superscript note references but it adds extra verbosity
(assistive technologies will announce the text is superscripted in addition to being linked).
vertical-align property can be set to superscript the
elements without the additional voicing (see Example 3).
Until there is greater support for announcing the
doc-footnote role, the
sup element provides some context for the note references. As support for the
role increases, however, the use of explicit superscripting will become redunant. At that
time, preference should be given to CSS formatting.
Although not specifically required to be accessible, it is good practice to backlink groups of notes to their referent locations in the text (see Example 4). If a user is surveying the notes, backlinks will allow them to quickly find the text the note refers to.