To www or not to www in Apache
non-www to www using .htaccess
RewriteEngine On
RewriteCond %{HTTP_HOST} !^www\.
RewriteRule ^(.*)$ http://www.%{HTTP_HOST}/$1 [R=301,L]
www to non-www using .htaccess
RewriteEngine On
RewriteCond %{HTTP_HOST} !^my-domain\.com$ [NC]
RewriteRule ^(.*)$ http://my-domain.com/$1 [R=301,L]