301 Redirect non-www requests to www.yoursite.com
This is to help with your SEO
use an FTP client to log into the main WWW root or Public_Html [depending upon your host]
find the file called .htaccess [make sure its writable by checking the CHMOD attributes]
add these lines to your .htaccess file
Options +FollowSymLinks
RewriteEngine on
RewriteCond %{HTTP_HOST} ^yourdomain\.com
RewriteRule ^(.*)$ http://www.yourdomain.com/$1 [R=permanent,L]
remember to replace yourdomain.com with the actual name of your domain