If a website does not resolve when you type in "example.com" (without "www"), then it probably means that the site does not have it's "Host name" site bindings configured correctly to except (non-www version) requests to "mydomain.com". Instead, they probably only have configured the Host name "www.mydomain.com". Adding in a second Host name for the non-www version of a site can easily be configured using Internet Information Services (IIS) for all websites.
On the other hand, if the website is automatically redirecting from the non-www "example.com" to "www.example.com", then this would most likely mean that the website administrator configured the site to redirect any requests from the (non-www) website domain, to go to the unique address at "www.example.com". This is actually good practice, and helps a site get better SEO rankings, because having different url paths go to the same page is considered bad in the eyes of search engines. For example, the following are all considered different url's in the eyes of search engines like Google, however all the urls could potentially be setup to go to the same home page:
■ www.example.com
■ example.com/
■ www.example.com/index.html
■ example.com/home.asp
So essentially, you want to choose one url structure and use that for all urls. Take a look at what happens when you go to
http://gotknowhow.com (or any page on gotknowhow.com without the "www".) You will automatically be redirected to the "www" version of the page...
http://www.gotknowhow.com (this is good practice). See the second link below to learn how to set this up in IIS7 using the URL Rewrite Module.
Source(s):
Matt Cutts on SEO advice: url canonicalization -
http://www.mattcutts.com/blog/seo-advice-url-canon...
Redirect to WWW of a site using IIS URL Rewrite Module -
http://www.gotknowhow.com/articles/how-to-redirect...