Because this website doesn't use SSL (Secure Socket Layer, which results in the https protocol being used), that warning is now generated in browsers. It's always been that way since the site started but only recently have browsers started showing the warning.
When data is passing back and forth from the BibleSupport server to your computer, it can pass through many servers and networks. Because we don't have SSL, logins and passwords are sent as plain text (unencrypted). Since we're not a bank and we don't handle financial or sensitive information, I never saw the need for it.
However, it's now considered good practice to use encryption because some people use the same login and password on every site. If a hacker picked off such a person's credentials, they could have access to all of their accounts on all of their websites. Of course, there's obvious security concerns with someone using the same password on every website but people do that. And the browsers showing that warning is designed to force site owners to update to SSL to cover for people who use the same password on every site. And I'll do that one of these days.
When I signed in to my BibleSupport account and got to the password field, there was a Firefox message saying the connection was not secure and my login could be compromised. I don't know how accurate that message was. Here's a link to info on this subject.