> <http://fr.download.sketchup.com/OnlineDoc/gsu6_win/g>
> suwin.html
>  
> I tried many options; it does not seem to me it's a
> particular site; is it its form with contents which

There are no links on the page. The entire left menu is all generated by
javascript which Httrack can't handle.

If an individual frame had links, you could mirror the frame, but most do not
link to others (no next page buttons.)  

For example, if you click on the menu "Dessiner dans SketchUp", and then (on
the main frame) right click/show this frame only, the url is
<http://fr.download.sketchup.com/OnlineDoc/gsu6_win/Content/A-Welcome/Concepts/Con-Designing.htm>

This Httrack can get along with the links contained therein.