If @domain is empty, then don't postfix dot to @domain

The intentional message which appears like this:

... To log into this site, you need to accept cookies from the .subdomain.domain.com

The dot which is prefixed to the (sub)domain should not be there.
Quote from the file 'cookie_check.module':
form_set_error('', t('It seems your browser does not accept cookies. To log into this site, you need to accept cookies from the domain @domain.', array('@domain' => $domain)));
I think there should be some "IF @domain is empty, THEN don't postfix dot" in there somehow.

Furthermore, I suggest to change the message, like so:

Your web browser does not accept persistant cookies.
To log into this site, your web browser needs to accept persistant cookies from the domain {domain}