Its ok - the reason you are getting the error is your browser has a built in list of certificate issuers that it trusts to issue SSL certs … i.e. godaddy, verisign etc. The cert for www.inscom.army.mil is issued by DOD ID SW CA-37 which isn't in your OS/browsers pre configured trust list hence the error.
tl:dr if you trust www.inscom.army.mil you are fine to proceed.