If you have some time to invest, I would go for DocBook. The html Version of DocBook: The Definitive Guide by Norm Walsh and Leonard Muellner (O'Reilly, 1999) is available for free at O'Reilly's page, for easy browsing, or as a zipped download from docbook.org (html or sgml). Browsing a while through DocBook: The Definitive Guide should give you enough information to decide, wether this kind of encoding is the right stuff for you.

Hanamaki