To fix this problem, do the following:

- Update to the current SVN revision 4368 of mhttpd.c
- Add following tag into your custom page:

  <input type=hidden name="redir" value="name">

  where "name" is the name of your custom page which follows the CS/ in the URL. Like 
if you have a custom page which you access through httpd://localhost/CS/junk then the 
tag would be 

  <input type=hidden name="redir" value="junk">

The "redir" parameter is now evaluated inside mhttpd and brings you back to the proper 
custom page. You can also define another custom page as the target, if that makes 
sense in your application.

Pierre: Would be nice to document this somewhere more officially.