This is documentation about a configuration directive, which can be placed within Movable Type’s core configuration file,
mt-config.cgi, to customize the behavior of the system.
This optional value specifies a domain within which the cookie applies. Only websites in this domain will be able to retrieve the cookie. Usually this is left blank, meaning that only the domain that set the cookie (the domain of the published site) can retrieve it.
To allow cookies for all sub-domains on movabletype.org the value is “.movabletype.org”: