The history of writing is push and pull between the writer and the reader. Shorthand, abbreviations and acronyms convenience the writer at the cost of decreased legibility; spaces, punctuation and paragraph breaks hasten comprehension while decelerating writing.
However, abbreviations do have some value for the reader. It can be laborious to repeatedly scan “United Kingdom” when “UK” will do. In print, it is important to weigh the benefit gained from abbreviating against the possible confusion caused for readers.
On the web, however, any confusion caused by abbreviations is gone.
By using the abbr tag, it is possible to display the abbreviation but give the option to read the full text by hovering the mouse over.
With this tag, the benefit from abbreviations swings completely towards the reader.
This means that if your priority is pleasurable reading and you are typing your own HTML, there is no reason not to use the tag for all your abbreviations.
And I mean all of them.
It is especially infuriating when articles about the abbr tag don’t even use it.
The web is a new medium; why not spell out abbreviations this way?
Even using the tag for Latin phrases like “i.e.” has educational value, if nothing else.