That's impossible. You're going to need a backend, which at that point it stops being HTML+CSS and becomes LAMP or something. The only thing I can think of tha

That's impossible. You're going to need a backend, which at that point it stops being HTML+CSS and becomes LAMP or something. The only thing I can think of that can be done in pure HTML+CSS that would drive any sort of revenue and could be considered a business is an affiliate marketing site. I suppose you could also run a survey site and collect feedback via mailto link, but that's really old school.