There's no need to worry. The below should address your concerns. The first Microsoft Support article explains what the message means, and how to stop it from appearing, if that's what you're trying to achieve. (As does the other)
“Only secure content is displayed” notification in Internet Explorer 9 or later
Why does my browser warn me that “Only secure content is displayed?”
According to your profile, Windows 7 is your operating system. There's a post at the Windows Seven forum, which includes a screen capture of the settings change. I would suggest first reading the above articles, in order to better understand what the message means.
Best of luck,
Recently this information bar appears at the bottom of my screen: "Only secure content is displayed" It then provides me a section to click on if I want to "show all content". This bar appears when I am accessing Yahoo and or Yahoo email? It is extremely worrisome and I cannot figure a way to stop it from appearing. It serves no real purpose.
Has anyone else noticed this information bar appearing at the bottom of their screen - and if so have you found a way to prevent it?