If a server is sending `Strict-Transport-Security: max-age=0`, SSL Server Test reports "Unknown" next to the HSTS line in Protocol Details.
I feel like this messaging could be improved. Maybe something like this?
max-age=0 DE-LISTING REQUESTED (more info)
And then link to here for more info? https://tools.ietf.org/html/rfc6797#section-6.1.1