White Screen Flash When Opening Firefox 60 or 61

Have you tried opening Fx in Safe Mode, to see if the cause might be an extension?

Josey Wales said:

It is not an extension , I tried it without any extensions installed, But thanks for the replay! This is a new thing with Fx 61 using the default Dark theme. I hope it gets better as I am only on BETA 4.

I believe that I have seen similar postings, and not necessarily with beta-test versions, so I suggest that you try other themes, to see if you can isolate the problem. As I wrote, I have a feeling that I have seen this problem mentioned, but can offer no specific proof to that effect, nor will I take the time to try to find any relevant posts.

Josey Wales said:

It is just a minor annoyance, it has been an issue with Firefox for years. This Dark Default theme is new for Firefox and it does make the entire default Home dark.

The Dark theme was introduced with the first release of Fx Quantum (57.0) as I recall, and it may well have been some references to that theme causing problems that I sort of remembered. At any rate, I suggest at least trying the Light and Default Fx themes.

Josey Wales said:

Yes it was but at that time it did not make the entire page DARK

I just tried Dark for the first time since the first day of Quantum; it works correctly with Fx 60.0, which is why I suggest that you try the other two themes, to see if there is a common problem or if it applies only to Dark.

in absentia lucis, tenebrae vin**** in the absence of light, darkness prevails (I see that the censor has removed the end of the Latin expression! Rather silly, prudish, or `whateverish'.)