Google treats www.website.com and website.com as two totally different websites. This is very bad for your (or even a client’s) website as it may lead to duplicate content and different pageranks to those sites. This is how Google “canonicalizes” the url and is very bad from an SEO standpoint.
In essence, a web server could return totally different results for each of those pages. I have also encountered the situation where clients have set their preferred domain in Google webmaster tools, have given out the opposite version for SEM and wonder why they don’t see results :)You can easily check the above by using the “site:” operator in Google search. E.g. site:www.website.com and site:website.com
You can use “mod rewrite” rules as a powerful method for redirecting many URLs from one location to another. This is a simple server level technique for handling redirects. The way people handle this canonicalization issue is purely a personal choice, although the below method can be altered for directing to the none www version of the url.
The .htaccess file is simply an ASCII file created with any normal text editor. You need to save the file as ‘.htaccess’ (no filename, .htaccess is the extension!). Open you newly created .htaccess file in your favoured text editor and add the following lines of code, replacing domain.com with your domain:
RewriteEngine On
RewriteCond %{HTTP_HOST} ^domain.com
RewriteRule (.*) http://www.domain.com/$1 [R=301,L]
Upload the .htaccess file to the root folder of your website and you’re done. All your traffic will be permanently redirected from a non-www version of your website to a www version of your website. To do the opposite (direct all traffic to the non www version use the below code in the .htaccess file):
RewriteEngine On
RewriteCond %{HTTP_HOST} ^www.domain.com
RewriteRule (.*) http://domain.com/$1 [R=301,L]