Some websites use different www# to point to different server clusters. Something like: www.domain.com = Server Cluster 1 or DC1 www2.domain.com = Server Cluster 2 or DC2 www3.domain.com = Server Cluster 3 or DC3 While there are "better" ways of setting this up each website/company has its own way of handling things. Its no different version of the internet or anything so spectacular. Note: DC above stands for datacenter or a building designed to house servers.
Thanks, I wondered that too, but noticed it changed at different times, so I thought it might be due to the server.