YaTeX automates typesetting and previewing of LaTeX and enables
completing input of LaTeX mark-up command such as `\begin{}'..`\end{}'.
YaTeX also supports Demacs which runs on MS-DOS(386), Mule (Multi
Language Enhancement to GNU Emacs), and latex on DOS.

Yahtml is a brand new package for writing HTML files with Emacs. It is
very far from html-mode, html-helper-mode or other existing HTML modes.
It is a good successor of YaTeX in HTML world.