Hi, where does this banner appear? For example:

• "Home" page in a new window (Ctrl+n) or when you click the house icon on the toolbar
• "New tab" page when you click the "+" icon on the tab bar or press Ctrl+t
• Every page you open

One possible culprit would be an extension. You can view, disable, and often remove unwanted or unknown extensions on the Add-ons page. Either:

• Ctrl+Shift+a (Mac: Command+Shift+a)
• "3-bar" menu button (or Tools menu) > Add-ons
• type or paste about:addons in the address bar and press Enter/Return

In the left column of the Add-ons page, click Extensions. Then cast a critical eye over the list on the right side. Any extensions Firefox installs for built-in features are hidden from this page, so everything listed here is your choice (and your responsibility) to manage. Anything suspicious or that you just do not remember installing or why? If in doubt, disable (or remove).

Any improvement?

You may also need to reset your home page: How to set the home page.

Thank you,

I reset my Firefox, and that seems to have taken care of the problem.

Thank you for reporting back!

The "Refresh" feature moves your old profile folder to your desktop inside an Old Firefox Data folder. I suggest keeping that for a week in case you discover anything important is missing after the reset.

(Background for other readers: Refresh Firefox - reset add-ons and settings)