You can check if you have a Push permission for suspect domain(s) like shown at the bottom of the message and revoke this permission. See "How do I revoke Web Push permissions for a specific site?":

• https://support.mozilla.org/en-US/kb/push-notifications-firefox

Thanks for the help. Your response showed me a whole other section of controls in this ridiculous maze of security and permissions! Unfortunately, there is no access to settings on the little screen that pops up. Following the directions provided and using link, I arrived at the page of specific permissions for the page in question (Yahoo News) and found that I could individually grant/deny a host of things. Unfortunately, no matter what I checked or unchecked, there was no "save changes" type of option. Each time I would check to remove permissions (and 'push' was never listed) I would leave the screen and everything under the sun would be reauthorized automatically. I finally gave up and returned here.

Opening a fixed mini player automatically is a feature offered by the website and is created via JavaScript if the main player is scrolled out of view. A lot of websites now have a fixed (pop-up) mini player in one the corners once you start playing a video that stays visible if you scroll the page.

You can look at these prefs in about:config to see what settings work for you to block media auto-play.

• media.autoplay.default = 5 [0:allow;1:blockAudible;5:blockAll]
• media.autoplay.blocking_policy = 2
• media.autoplay.allow-extension-background-pages => false
• media.autoplay.block-event.enabled => true
• media.block-autoplay-until-in-foreground

You can open about:config via the address/location bar. You can read the warning and click "Accept the Risk and Continue".

• https://support.mozilla.org/en-US/kb/about-config-editor-firefox

• https://support.mozilla.org/en-US/kb/block-autoplay

You can use an extension like PopUpOFF to hide sticky video elements.