It seems like every time I reinstall Firefox, or start over with a new profile, this problem comes up, where an Ffx window flashes white for a moment, between the closing of one tab in favor of another.

And every time, I forget what the fix is, so off to Google. The best solution seems to be the one where you put this into a new Stylish (script) or into userchrome.css

@namespace url(“…;
/*Prevents White pre-load flash*/
tabbrowser tabpanels { background-color: black !important; }


That thing got partly linkified by kinja. Copy/paste as plain text.

This is probably not an issue if you use a white or some other light background, but if you like black as I do, that white flash can irritate. Hope you like.