Are there any versatile Emacs modes for HTML5 and HTML 4.01?

Question

I have very specific requirements:

• HTML5 and HTML 4.01 in SGML mode (I'm one of the non-believers in XHTML);
• Be able to mix in other modes (like Django templates, PHP, etc.)

Bonus points for validation and other development tools.

nxhtml is great and all, but it's pretty much entirely XML-based. I'm not working in XML.

Answer 1

I have historically used PSGML mode for editing HTML, and it works admirably well. It has a built-in parser, but it's somewhat limited: you can configure it to use an external SGML parser for more thorough parsing and validation. Installation and configuration is a bit tricky, but the user manual is reasonably well written and covers what you'll need to set up the various bits and pieces you need (Emacs + the PSGML mode elisp files + the appropriate SGML declaration, DTDs, entity files + the SGML parser you want to use).