Its not the domain name, but the SSL certificate that the site is using, you may not see it cause you have already choosen to accept it permanently and MSIE doesnt ever report back when certs expires, but for us 'enlightened Firefox users' that goes to the website for the first time gets a popup notification dialog window that asks if we want to accept this cert and it does also ask if we want to accept it since it has expired.
See photo:
