In the SEO world, there is an issue which exists called the Canonical Problem.
Sounds like something to do with the Pope, right?
Well, it’s a simple issue, related to how web addresses work and usually only found when dealing with older websites where people created links with and without www. If you have this problem, then you need to understand that in the world of URLs, domain.com and www.domain.com are two different web addresses and this may be evident when you see them listed on reports for such popular tools as Google Analytics or SEOcentro or in search results for such engines as Yahoo or Google. This is normal, but not desired from an SEO standpoint.
To test how your links appear, Google for this: site:mitchellenright.com (replace your domain name for mine)
If you see your domain listed with and without www then you have a canonical problem.
To correct it, you will need to rewrite your URLs via the webhost.
URL REWRITES
If you have an Apache server, then this is the code you add to your .htaccess file to facilitate rewriting domain.com to www.domain.com:
RewriteEngine On
RewriteCond %{HTTP_HOST} !^www\.domain\.com$
RewriteRule ^(.*)$ http://www.domain.com/$1 [R=301,L]
If you have an IIS server, follow the instructions here:
http://www.iis.net/URLRewrite
In short, this is called a 301 Redirect, and these can be used for much more than just what I listed above. More information about 301 Redirects can be found here , here or here. One of those should work for you.
NOTE: If your website does not resolve at all when accessed via domain.com and not www.domain.com then you will need to add an entry to DNS. Create a blank A Record with the IP address of the web server. More information on this subject HERE
NOTE: If you’re running WordPress, then you want to make sure your blog address matches what you’re redirecting to, or else you can enter into an infinite loop.
