The WHOIS info of a domain is a collection of many details which are freely accessed through specific lookup websites or a command line. The protocol which makes this possible has the same name and you can very easily see the firm through which a domain address has been registered, the creation, expiration and last update dates along with the names, postal and e-mail address of those listed as Registrant (owner), Administrative, Technical and Billing contacts for a particular domain. This info ought to be valid and up-to-date constantly; if not the domain name registration may be challenged. The latter is a policy of ICANN (the Internet Corporation for Assigned Names and Numbers), therefore you must always ensure that the WHOIS details of your domains are valid. Updating the WHOIS for several country-code TLDs is limited, so when you register a completely new domain address, it is best to double-check the information that you are submitting.