MWE
\documentclass[]{article}
\usepackage{cprotect}
\begin{document}
\cprotect\fbox
{
\begin{minipage}[t]{\textwidth}
This is a test
\end{minipage}
}
\end{document}
compiled with htlatex foo.tex
generates this html
The HTML is
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html >
<head><title></title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="generator" content="TeX4ht (http://www.tug.org/tex4ht/)">
<meta name="originator" content="TeX4ht (http://www.tug.org/tex4ht/)">
<!-- html -->
<meta name="src" content="foo.tex">
<meta name="date" content="2015-03-10 14:04:00">
<link rel="stylesheet" type="text/css" href="foo.css">
</head><body
>
<div class="fbox"><div class="minipage">This is a test</div> ˆˆEˆˆL</div>
</body></html>
file list
*File List*
article.cls 2014/09/29 v1.4h Standard LaTeX document class
size10.clo 2014/09/29 v1.4h Standard LaTeX file (size option)
tex4ht.sty
cprotect.sty 2011/01/27 v1.0e (Bruno Le Floch)
ifthen.sty 2014/09/29 v1.1c Standard LaTeX ifthen package (DPC)
suffix.sty 2006/07/15 1.5a Variant command support
***********
texlive 2014 on Linux. I will also post this to tex4ht mailing list. This looks like a bug. Just posting here for reference or if anyone has an easy workaround. (there is no tag for the cprotect package)
)