.htaccess – how to force “www.” in a generic way?
I would use this rule: The first condition checks whether the Host value is not empty (in case of HTTP/1.0); the second checks whether the the Host value does not begin with www.; the third checks for HTTPS (%{HTTPS} is either on or off, so %{HTTPS}s is either ons or offs and in case of ons the s is matched). The substitution part of RewriteRule then just merges the information parts to a full URL.