Sometimes an otherwise secure website may fail to provide a secure way to submit a form, such as a form that contains your password or credit card number. Safari displays a message if you’re about to send information in a nonsecure way, so you can cancel. If you don’t want to see this message, you can turn it off.
Choose Safari > Preferences and click Security.
Deselect “Ask before sending a non-secure form from a secure website.”
If you turn off security warnings, you lose some of your protection against Internet risks. Share personal information and download items only if you are certain that the website you are visiting is trustworthy.