The certificate just expired, or was replaced with a certificate that expired ages ago. So the site is no longer reachable.

Edit: The site's back. There was a temporary problem with ssl proveder or the server itself but now everything's back and is working, no more errors like that.

I cannot connect to kyselo using my internet connection. It appears the domain expired as it seems the browser is struggling while trying to find the site.

Update: Kyselo back up.