> I have copied a web site and view it afterwards locally.
> Everything looks ok except that some Internet traffic 
> still occurs each time I view a new web page.

I don't think you can exclude those javascript ads with 
HTTrack -- they're not dealt with as a link but inserted 
when you browse the page.

Also, they clearly say:

NOTE: Using software to mass-download the site degrades the 
server and is prohibited. If you want to read The TCP/IP 
Guide offline, please consider licensing it. Thank you.

You would have to use a tool to do regular expression search 
and replace to remove the script blocks.  But there are also 
<noscript> blocks which point to ads too.  It's complex.