This is a ddns provider. To add a subdomain, append URL parameters.

Example: /?domain=www2&ttl=600

Available parameters (some may have been disabled by the administrator):
    domain:    the subdomain to add a record for
    ip:        the ip address to add (uses your current IP if missing)
    password:  lock the subdomain with a password, which will be required to
               change the entries in the future
    ttl:       ttl of the record in seconds
    type:      record type, can be A, AAAA, MX, CNAME, etc

Source: https://github.com/thingless/ddns