For some reason, Firefox browser has started defaulting to a screen larger than my monitor.
If I hit the Full screen Box, it will adjust to the actual size of the monitor but when I hit return to normal it will again become large
ప్రత్యుత్తరాలన్నీ (2)
Do you mean the Fullscreen (F11, or in View menu) function, or the Un/Maximize toggle button (the one between Minimize and Close)?
If you can grab a corner in the unmaximized state, hold the Shift key and resize the window. Let go of Shift. Close Firefox. (Some people swear that using the Quit function in the File menu, or Firefox menu, the equivalent of ctrl+q, is better than using the close window button [X] when doing this.)
Restart Firefox and see if your window behaves.
Try to rename/remove xulstore.json in the Firefox profile folder with Firefox closed.
You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.
- Help -> Troubleshooting Information -> Profile Folder/Directory:
Windows: Open Folder; Linux: Open Directory; Mac: Show in Finder - https://support.mozilla.org/en-US/kb/Profiles