> I take it a website can employ a filter to prevent 
copiers 
> like HTTrack from functioning.  How do they do that if 
the 
> copier or Offline Browser is mimicing a user?  Where 
could 
> I go to learn more about website administration and 
> management and the specific use of such filters?>  Are these 
> filters commercially available or built in to server 
> software?
See <http://www.httrack.com/html/abuse.html#WEBMASTERS>