My wife does facebook much more than i do.
The other day she said to take a look at whatever, and up popped a box [I think] stating you could ease eye strain be changing to black background.
I did - not really thinking ! Like if you want to print something you get a black page with white print - great for consuming toner!
Cannot for the life of me find where to change the setting back to white background.
Home computer Win 7, laptop Win 10 operating systems.