Why redirect if both URLs work fine without it?

Search engines consider http://wpthemesgallery.com and http://www.wpthemesgallery.com as two difference websites. So, when other websites link to you, they might not all choose the same URL, splitting the link popularity of your website. By 301 redirecting, this is fixed, and the link popularity from both URLs are combined into one.

How to redirect?

These are the instructions of how to redirect on an Apache server:

1. Download the .htaccess file from your website’s root folder;
2. Add the following code to it:

RewriteEngine On
RewriteCond %{HTTP_HOST} ^wpthemesgallery.com
RewriteRule (.*) http://www.wpthemesgallery.com/$1 [R=301,L]

3. Replace wpthemesgallery with your website’s URL;
4. Replace the old .htaccess file with the new one.
5. Try visiting the non-www URL and if it redirects to the www URL, you’re done!

If you are using WordPress and have been getting errors after the redirect, do the following:

1. Log in to the admin section of your WordPress blog;
2. Click on Options;
3. Add www to the WordPress address and Blog address URLs.

This should work and now you won’t get any more errors that were caused by the redirect.