I was not clear.

That's what I did. I did a configure/make/make install

I launched webhttrack and it complained because it could 
not find files in /usr/share/kde/httrack/web (if I'm 
correct)

anyway I copied all the .php files in that directory, which 
is obviously OUTSIDE my web root directory in /var/www

I guess that's why Mozilla goes "outside" on the web. It 
can't find pages not managed by my local Apache