> Through the experiment, when the Dynamic Content
> Compression function of  web server IIS is closed,
> HTTrack Version3.48-10 will not repeat the update no
> changed webpage.
> Because of the different each time compression ratio
> on MS IIS , even if the web page content did not
> change, but the web server send to the client's data
> is still not the same, which can be considered to be
> different. 

HTTrack is using standard HTTP mechanisms for updating:
  * If-Modified-Since
  * If-None-Match

The actual size of bytes sent is *only* a hack implemented in httrack as a
workaround for servers not fulfilling the update request properly.

If the compressed data size can change, there is unfortunately no way to solve
the issue, I fear.