Firefox 143.0.3 on Windows 11 24H2. I normally run my browser window full vertical height of the screen (but not maximized). If my PC goes into screen save due to lack of activity, each time I return and it comes out of screen save, the bottom of the Firefox window has risen vertically by about 15-20 pixels, and there is now a gap between the bottom of the FF window and the bottom of the screen. If I go in/out of screen save again, then the gap increases again as the windows shrinks further. The top of the FF window doesn't move, only the bottom. This problem doesn't happen with the window size of any other app that I use if I size the window the full height of the screen and go in/out of screen save - eg the Thunderbird window remains the full height of the screen. Any suggestions on a possible cause and how to fix the problem? It isn't just the latest version of FF that has the problem - it was also there with previous versions.