What does this message mean?

[Marcia]

When I send email from my hotmail account, one person gets this message before she can even see my email:

Security warning: Do you want to view only the webpage content that was delivered securely?

This webpage contains content that will not be delivered using a secure HTTPS connection, which could compromise the security of the entire web page. (more information) (Yes) (No)

I look at the address bar of my hotmail account, and I see HTTPS on it. It used to didn't have it.

[Ramón]

Try updating your web browser or install a other.