Hard drive crash. iWeb empty. Site hosted. How to get them back?

Backup. Time Machine.

Default location :

~/Library/Application Support/iWeb/

Lost domain files and how to get them back is often discussed in this forum.

Here's such topic :

https://discussions.apple.com/thread/4879606?tstart=0

iWeb can't import your pages and files. It works with its own special file that stores your files and data input and only generates the page code when you publish.

You'll need to recreate your pages. Since you still have the page code and other files you can use copy/paste from a browser to iWeb.