You can try to disable hardware acceleration in Firefox.

• Tools > Options > Advanced > General > Browsing: "Use hardware acceleration when available"

You need to close and restart Firefox after toggling this setting.

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

• https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration

Is it the web site, or the Firefox menu?

Also, please update all of your Adobe.com software.

It's both. For example if I'm on a YouTube page and have searched for something and tight click on a hit to open it in a new tab, it disappears. Similarly if I then go to the Firefox File menu to looks at my plugins, that will disappear to as I move the mouse down.

It does fix itself if I close the current tab. I'll update Adobe as you suggest and also do the hardware acceleration stuff suggested.

It's the most annoying bug I've ever encountered, even more than the Microsoft update bug that corrupted fonts a few months back and prompted me to turn off their updates entirely since they just didn't seem to fix it. It took me ages to locate the relevant update in that case. Believe me, we unfortunate not very nerdy users don't appreciate this sort of thing the slightest bit.

Thank you for your responses.

Start Firefox in Safe Mode {web Link} by holding down the <Shift>
(Mac Options) key, and then starting Firefox. Is the problem still there?

Hi Fred. Thanks for contributing. The problem is not straightforward to replicate, but it seems to happen most on Youtube and indeed has happened to me today after trying both previoius suggestions (i.e. disabling hardware acceleration and updating Adobe Flash).

I did just now just try using safe mode and it didn't replicate on loading a YouTube page, so that looks like progress. I will look throiugh the relevant guidance there to see if I can locate it.

One thing I do remember doing was turning on "always allow this site to use ...(something which lets you run a video - I think Adobe Flash )" for YouTube. I had set that to "Activate on request" because probably the most annoying perennial problem with Firefox is that it inevitably screws that up with every single update. I typically get problems with scripts for ever locking you out of Firefox until the alloted period of virtually infinite time the software designer allocated to the process before telling the customer something's up has played itself out and condescends to allows you to stop the script.

If someone with an advanced degree in Firefox could tell me how to reset that back to "Activate only on request" for YouTube that would be useful. Meanwhile I propose to add YouTube to a growing list of websites I no longer open in Firefox.

As I say, it's excessively frustrating. Twenty minutes alone responding here - not good and time to think about bailing out for good methinks. Love Firefox, but this is hell. Thanks for your time anyway Fred.

OK Fred. It's definitely YouTube causing this problem, presumably because I allowed Firefox to activate Adobe Flash automatically on YouTube. If I load this particular YouTube page and then try the upper left Firefox Menu and move the cursor down and to the right to inspect say Options the menu disappears. If I close the YouTube tab everything is OK again.

So how do I restore "Activate only on request" to YouTube for Adobe Flash. I did update Adobe this morning. One of the problems we mere customers without higher degrees in Firefox have, is that when we look at the Extension page in Options, there's no mention of Adobe Flash we can see.

I think it's Classic Theme Restorer that's the problem. I can't really tell because when I disable it, the drop down menu structure changes anyway and you can't move the mouse across to sub-menus which was causing the problem anyway.

Buit that's my best guess. So now i will have to waste time learning new stuff about Firefox in this appearance I really don't like and can't be bothered with but which some Firefox Nobel Laureate insists on shoving up my back passage anyway because he/she knows better than me what I really should like. Right now don't even know how to open a new Tab, supposing I could even decipher what a Tab actually is in the new Nobel prize winning dispensation.

God, I do wish software engineers would stop trying to fix problems that weren't broken in the first place. This has been so quite fantastically ANNOYING.

Thanks Fred and others for your time.

Install this add-on, then surf as you normally do.

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

Thanks Fred. I'll give it a go. Appreciated.