The macro \htmlfootnotemark{n} typesets the mark that
is placed in the text as a hyperlink to the footnote text. See the
file siteinit.hlx for the default definition.
The environment thefootnotes generates the HTML node with the
footnote text. Every footnote is formatted with the macro
\htmlfootnoteitem{n}{text}. The default
definitions are
\newenvironment{thefootnotes}%
{\chapter{Footnotes}
\begin{description}}%
{\end{description}}
\newcommand{\htmlfootnoteitem}[2]%
{\label{footnote-#1}\item[(#1)]#2}