Interesting situation. It is possible that there is some redundancy that is causing the server to be backed up elsewhere on your network (for example if you are in a Windows domain forest, there may be a failover that makes the site accessible on another server) or it is possible that you get routed differently internally. If you would like, I could try to track it down for you. Just PM me with the domain name, and the IP address that it currently shows up as being on, and I can try to find where the site actually is.

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The best way to learn anything, is to question everything.