I would suggest to use DocBook instead of HTML for documentation. DocBook is XML based format that was specifically designed for technical documentation writing. It is easy to convert to any other format that you might need, such as HTML, PDF, PostScript, text, etc.

If you would have been using DocBook, then your problem could have been easily solved. Look, for example, here (Chapter 1 of "DocBook: The Definitive Guide" by Norman Walsh and Leonard Muellner). Scroll down to "Marked sections" to see an example (specifying Draft parts of the document). You can also use the rest of the book to find a number of good reasons to use DocBook instead of HTML. :)

My 2 cents.