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They're the same site but not the same url.  Notice one of those URLs begins with www and the other does not.  It's just a weird thing about the way internet servers are set up and having problems with which one of them should be the one you use is called a canonicalization issue. Most webmasters chose to use the www version and redirect the non-www version to it via settings on the web host.  Here's some more reading on canonicalization.