It's a warning generated by browsers when your website is using an unsigned SSL certificate that our system may have generated for you when your website was first provisioned, or if your SSL certificate has expired.
While there's nothing wrong with your website and its security, if you would like to have this warning, please contact our team to purchase a signed SSL certificate. (see our SSL pricing page) or have us install a valid default certificate.
We require SSL on all admin panel sessions in order to protect sensitive information about your website, but we don't necessarily require a valid certificate for this functionality.
Please contact support if you have trouble getting in to your admin panel.