I wonder how much example.com would sell on auction? It's a PR8 and it had no content
In the DNS settings, www is entered as a sub domain. But what xxtoni says above is the reason why it is not a normal sub domain, it is treated as if it is present or not in the same way.
I just did a simple test on one of my older sites that has good PR and Alexa Rank and the figures for PR and Alexa rank are the same for all 4 combinations of:
But the PR for:
blog.site.com is completely different (Alexa rank the same).
So in this case blog.site.com is being treated as a different website by Google. But Alexa seems to only look at the TLD.
You have reached this web page by typing "example.com", "example.net","example.org" or "example.edu" into your web browser.
These domain names are reserved for use in documentation and are not available for registration. See RFC 2606, Section 3.
www is actually a subdomain, not a prefix.www is a prefix
PageRank is applied to each page or each URL, and since Example Web Page and example.com are two separate URls and two separate pages, then they can have different PR.
Usually that's the case, but it is important to "pick one" and set up a 301 Permanent Redirect from one to the other. And don't forget to set your preferred domain in Google Webmaster Tools, as well.most often Google resolves the canonical issues on its own.