Redirect non www record to www record via .htaccess

To avoid search engines indexing your site under the www record and non www record, you can redirect the non www record to the www record. From a user point of view this means that when I browse to domainname.com, I am redirected to www.domainname.com.

Create a .htaccess file
Add the following lines to it, replacing domainname.com with your domain name:

Options +FollowSymlinks
RewriteEngine on
RewriteCond %{HTTP_HOST} ^domainname.com [NC]
RewriteRule ^(.*)$ http://www.domainname.com/$1 [L,R=301]

Place this in your webroot folder

You can use this to also redirect domainname.com to any-other-address.com if you want, just replace http://www.domainname.com/ with the URL you want domainname.com to point to.