Here is a discussion about the Difference Between HTTP and WWW
There are some websites that open only when you type http://anything.com
Those sites do NOT open if you type http://www.anything.com
That means, some sites just do NOT work if you use www; you have to type http only, without typing www
So, what’s the real difference between http and www in this situation? How come some sites work only if you type http but not www? And base on SEO, Backlink Building, and Indexing on Search engines, will there be any effect on a blog formally opening as http://anything.com then changed to http://www.anything.com.