Accessibility - Refactoring HTML: Improving the Design of Existing Web Applications - page 234

Introduce Acronym Elements
Wrap abbr and acronym tags around abbreviations and acronyms.
<label>Subject:
Gleaning Resource Descriptions from Dialects of Languages
(GRRDL) defines Extensible Stylesheet Language
Transformations (XSLT) stylesheets that can transform
Hypertext Markup Language (HTML) documents into Resource
Description Framework (RDF) triples.
<acronym title="Gleaning Resource Descriptions from
Dialects of Languages">GRRDL</a> defines <abbr
title="Extensible Stylesheet Language
Transformations">XSLT</abbr>
stylesheets that can transform <acronym title="Hypertext
Markup Language">HTML</a> documents into <acronym
title="Resource Description Framework">RDF</acronym> triples.
Motivation
Screen readers need to know when they should try to pronounce an entire word and when they should just spell
it out.
Not all your readers necessarily know all the acronyms that you use. Many browsers will show a tool tip to tell
the reader what the acronym means if you mark it up appropriately in the source document. This avoids the
need to explain everything for the larger portion of your audience who does know what the acronym means.
Potential Trade-offs
Some browsers put some really ugly dotted lines under marked-up acronyms and abbreviations. This also
throws off the line spacing. However, you can counter this with CSS.
Mechanics
For purposes of HTML, an abbreviation is made up of the first letters of the words in a phrase. It is pronounced
by spelling out the words. For example:
<abbr>BBC</abbr>
<abbr>GNP</abbr>
<abbr>IBM</abbr>
By contrast, an acronym is normally pronounced like a word, rather than by spelling it out. Examples include:
<acronym>NAFTA</acronym>
<acronym>GATT</acronym>
<acronym>Inc.</acronym>