We switch to a secure server for applications which require credit card details.

The following is to clarify what you see on the screen when you enter an application running on the secure server - for the present it will be when using an event Online Entry Form. I'll reference Internet Explorer.
 
Entering Secure Server
This message may be displayed when you enter the secure server.

You wont see it if you have previously ticked the box marked "In the future, do not show this warning".
 
 
Whether or not the dialog box is displayed, you will know that the host is a secure server, if you see a lock in the bottom right side of your screen
(in Explorer).
 
 
Leaving Secure Server
This message may be displayed when you leave the secure server.

Once again, you wont see it if you have previously ticked the box marked "In the future, do not show this warning".
 
 
Whether or not the dialog box is displayed, you will know that the host is no longer a secure server, if the lock in the bottom right side of your screen (in Explorer) disappears.