Indexes should be marked up using unordered lists, as the alphatized order of the entries is not significant (e.g., an index can be reverse sorted without loss of information). If page numbers are included in the publication, page references in index entries can be linked.
To faciliate navigating an index, use nested
section elements to enclose alphabetically- and
numerically-related entries. Many indexes include the number or letter as a heading, but if one is not
present or wanted, include the number or letter in a
title attribute on the enclosing
section so that it can be announced by assistive technologies.
The use of lists is recommended as it simplifies navigation by users of assistive technologies. Not only does it speed up the movement through entries, but the position within the list can be announced, allowing the user to quickly return to the same spot again later, if needed.