Why am I getting the no-lock icon on some Websites in Mozilla Firefox?

If you are visiting a Website that is using HTTP protocol with a certificate, Mozilla Firefox will display the no-lock icon instead the lock icon.

If you click on the no-lock icon, you see the site information dialog box displayed:

Site information for 192.168.1.1 

Connection not secure 

Clear cookies and site data...

Click the "Connection not secure" link. You see security properties displayed:

Connection Security for 192.168.1.1 

You are not securely connected to this site. 

Your connection to this is not private. Information you 
submit could be viewed by others (like passwords, messages,
credit cards, etc.).

More information

Click the "More information" link. You see the Page Info window displayed.

Website Identity 

Website: 192.168.1.1 
Owner: This website does not supply ownership information 
Verified by: Not specified 

...

Technical Details 
Connection Not Encrypted

The website 192.168.1.1 does not support encryption for the page you are viewing.
Information sent over the Internet without encryption can be seen by other people 
while it is transit.

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