If you are a webmaster definitely come across the warning by the browsers and not showing the Green Padlock at the address bar. If you found a Mixed content, definitely take it seriously and act as fast as possible to resolve the error.
Before coming into Mixed content, I would like to give a fair idea about HTTP and HTTPS.
The HTTP and HTTPS are both HyperText Transfer Protocol and HTTPS comes with secure access. Yes, everyone knows the HTTP is not secure and HTTPS is more secure and encrypted.
You are absolutely right, the HTTP is transferring the data from the server to the user browser through-plane text. Whereas HTTPS comes with encryption during data transfer. So everywhere we are digitally connected and web browsers are the primary source of intermediary, who accepts the web request from a web server to the user browser and vice versa.
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