> Hello, I need to copy a subdomain website and when I
> began the copy, an error immediately occurred with
> this message:

This is only a warning regarding an image which could not be found (probably
harmless)

> What does this mean? Is there anyway to make this
> work and copy a subdomain website with httrack?

You probably want to adjust the mirror scope, by modifying the Scan Rules, and
use something like:
+yoursubdomain.example.com/*