Your connection is not private
Attackers might be trying to steal your information from vimperator.org (for example, passwords, messages, or credit cards). NET::ERR_CERT_COMMON_NAME_INVALID
in Chrome.
According to https://help.github.com/articles/securing-your-github-pages-site-with-https/ - https is not supported on custom domains, but we should keep this open, to regularly check if that has changed.