Quote:
PROBLEM:
Firefox (FF) seems to forget on which screen it should start.
SOLUTION:
step 1) Reduce the size of the FF window with the "Restore Down" button. (It is the small button in the top right corner of the fullscreen window. Its icon is like two overlapping windows.)
step 2) Move the small window to the correct screen. Close the FF window. (Do not make it full screen yet.)
step 3) Open FF. It should appear on the correct window. Maximize it to full screen. Close FF.
Now it remembers where to open. (At least on the machines I have seen so far.)
Key to the solution is that it seems that FF saves its previous position only if it is not set to full screen when you close FF.