The Surveyproject.org website is making use of a SSL (secure socket layer) Certificate to offer secure HTTPS:// connections.
The SSL Certficate is issued by https://letsencrypt.org/ "Let’s Encrypt is a free, automated, and open certificate authority (CA), run for the public’s benefit. It is a service provided by the Internet Security Research Group (ISRG)."
Secure connections are used to encrypt any data sent from the webbrowser to the website and server (e.v.v.). In case of registering (personal) data a secure (https://) connection is enforced (e.g. user registration).
You can still access surveyproject over regular (unsecure) http:// connections (except for pages where https:// is enforced).
To fully benefit SSL security it is advised to access surveyproject.org over https://