Example for Checkpoint
4.2 - Specify the expansion of each abbreviation or acronym in a document where it first occurs.

When using abbreviations or acronyms in a sentence, be sure to indicate this in the HTML using ABBR and ACRONYM, like this:

When in Boston, be sure to visit the MFA, MIT and, of course, the W3C. These destinations are easily reached via Mass. Ave. or Mem. Dr..

And the markup would look like this:

Access Note: in the near future, browsers will let you choose to have the abbreviations and acronyms expanded automatically.

Or, provide the expansion (especially of the first occurrence) in the main body of the document (i.e. the way you would if you were not using HTML).