Accessibility - Refactoring HTML: Improving the Design of Existing Web Applications - page 235

These aren't quite the dictionary definitions of abbreviation and acronym —in fact, an acronym is really a type of
abbreviation—but they do reflect how speech synthesizers decide to pronounce each unfamiliar abbreviation.
Each abbr or acronym element should have a title attribute that expands the abbreviation. For example:
<abbr title="British Broadcasting Corporation">BBC</abbr>
<abbr title="Gross National Product">GNP</abbr>
<abbr title="International Business Machines">IBM</abbr>
<acronym title
="North American Free Trade Agreement">NAFTA</acronym>
<acronym title="General Agreement on Tariffs and Trade">GATT</acronym>
<acronym title="Incorporated">Inc.</acronym>
Some browsers will show a small tool tip with the title if the user mouses over the element. One big benefit is
that this avoids the need to explicitly define an acronym or abbreviation that 99% of people understand the first
time you use it.