I use GNU emacs for about everything and thus it shouldn't surprise that this also holds for producing HTML.
When writing ordinary web pages, the html-helper-mode comes in handy. I configured it such that it automatically inserts a reference to my style sheet to ensure consistency of the layout.
When I have already a LaTeX version of the web page to be made, I usually torture the LaTeX2HTML translator from within emacs, which is straightforward when using the AUCTeX package.