What value should I use for the "url-to-proposal"?

[kanguro]

Hi guys, I have one question in the CLI call to create a witness node:

create_witness <accountname> "http://<url-to-proposal>" true

What value should I use for the "url-to-proposal"?
Is that just any domain I own?
Is that a domain associated with my node?
Is that a domain associated with our Bitshares-ui?
Is that a domain associated with our business web site?
does the domain need to be up and available?

I have not found any description as to what that URL is supposed to refer to.

thanks