Is this Firefox's "missing plugin" notification, which I think appears in a bar that slides down between the toolbar area and the top of the page, or something that seems to be generated by the website?

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Here's a screen shot. Note that the "Varmint," as I called it, obscures part of the Firefox menu and part of the BBC News menu at the upper left corner of the screen. I don't mind if the average user likes to see this thing, but I sure would like to have the option of blocking it when I want to--which would be most of the time. It even rises from the dead if I close it but the screen later redraws. Grrr.

That is a built-in notification. Could you try changing one or both of the following preferences:

(1) In a new tab, type or paste about:config in the address bar and press Enter. Click the button promising to be careful.

(2) In the search box above the list, type or paste miss and pause while the list is filtered

(3) Double-click the plugins.notifyMissingFlash preference to switch it from true to false.

(4) If you don't want notifications for other plugins, double-click the plugins.hideMissingPluginsNotification preference to switch it from false to true.

I think that should hide the drop-down but still show the plugin notification icon so you can investigate page issues when needed by clicking on it. Does that work?

Install flash to keep them quiet. And install this;

Flash block {web link} Never be annoyed by a Flash animation again! Blocks Flash so it won't get in your way, but if you want to see it, just click on it

Have tried steps 1-3 and achieved apparent success on first trial. Don't know if altered setting will persist but will quickly find out through experience. Didn't fully understand need for step 4 and did not implement. Will gain experience with this solution before closing out topic. Thanks very much for helpful and speedy response.

This would be a solution of sorts, but I am trying to keep Flash (and its attendant drawbacks) from debilitating my system. Thanks for the idea.

FlashBlock does exactly that. NO flash will play unless you want it to.