> I got FORBIDDEN message in the browser. So, it works
> if a full string is given, but does not work to list
> the directory structure.
> 
> Can this be overcome by HTTrack ?

That's very common behaviour for a web server, and is to prevent browsing all
the files in particular directories.  And no, HTTrack can not get around this
security feature.

Here is some info on mirroring only images:
<http://httrack.kauler.com/help/Mirror_only_images>