> Is it possible to stop httrack re-downloding files that
> already exist (and are same size and/or date) on the 
disk? 

Normally httrack tries to limit the download, especially 
when using 'Update hack' option (which breaks the 
connection id the site is the same)

> It always downloads the whole site even though I select
> "Update".

- Check that this is actually the case: httrack has to send 
an update request for each file anyway, to ask if the file 
was modified
- The remote server might be refusing to fulfill update 
requests correctly