Pseudo code for how we authenticate that you can control listings for a domain:

IF domain is valid
	
	IF domain is found in our database

		IF today is <= expiration date

			IF file exists in your web root

				IF file contents are correct

					IF your workstation IP was authorized at time of last authentication

	(you get access to manage listings)

					ELSE offer option to re-authorize
				
				ELSE show instructions and proper file contents

			ELSE show instructions how and where to create file

		ELSE offer option to re-authorize

	ELSE offer form to add to our database expiration date, ip and preferred http port

ELSE offer option to correct domain name typo

END