I need to brush up on my internet protocols, but it likely has to do with the 'www.' not being included in the website name that was submitted to the DNS server. From what I recall, current internet protocols no longer require 'www.' to be included in the web address, and web designers can use whatever they want (nothing, www1., www2., ect.). Some websites have registered both with and without 'www.,' some have not.
*Patiently waiting for an actual cyber/tech guy to explain how radically I oversimplified that*