sorry, but what actually happened is that frank (mittelbach) actually updated multicol.sty, as his prerogative, of course. therefore eitan's hooks no longer do the right thing.

if i simply disable the \Configure{columnbreak}{auto}, well, the spurious "auto" doesn't appear, but the output isn't in two columns, either, as it used to be before TL'14.

how to change multicol.4ht to do the right thing with the new multicol.sty is a bigger job than i can tackle right now. michal, cvr?

btw, an even simpler document shows the problem:

\documentclass{article}%
\usepackage{multicol}
\begin{document}
\begin{multicols}{2}
before \columnbreak after
\end{multicols}
\end{document}

before tl'14, the output used <table> to make the columns. now that <table> is completely gone ...

details are here:
http://tex.stackexchange.com/questions/213527/htlatex-outputs-extra-word-not-in-document-when-using-columnbreak-with-multicol

summary:

MWE:

------------------------
\documentclass{article}%
\usepackage{lipsum,multicol}
\begin{document}
\begin{multicols}{2}

\section*{Introduction}
This is introduction
\columnbreak
\section*{my section}
This is my section

\end{multicols}
\end{document}
-------------------------------

htlatex output has an extra word auto in the output.

removing \columnbreak removes the word auto from the HTML page

Images can be seen at the above link. texlive 2014