Does this happen in other applications? We had a similar post the other day from another Windows 10 user (unsolved): [https://support.mozilla.org/questions/1204371 Window is moving down.]

[https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode Start Firefox in Safe Mode] {web link} by holding down the '''<Shift> ''(Mac=Options)''''' key, and then starting Firefox. A small dialog should appear. Click '''Start In Safe Mode''' (not Refresh). Is the problem still there? ----------------- Separate Security Issue: Update your Flash Player '''Note: Windows users''' should download the '''ActiveX''' for ''Internet Explorer.'' '''and''' the '''plugin''' for ''Plugin-based browsers'' (like Firefox). '''Note: Windows 8 and Windows 10''' have built-in flash players and Adobe will cause a conflict. Install the plugin only. Not the ActiveX. Flash Player Version: '''Version 28.0.0.161 ''' https://get.adobe.com/flashplayer/ Direct link scans current system and browser '''Note: Other software''' is offered in the download. <Windows Only> https://get.adobe.com/flashplayer/otherversions/ Step 1: Select Operating System Step 2: Select A Version (Firefox, Win IE . . . .) '''Note: Other software''' is offered in the download. <Windows Only> +++++++++++++++++++ See if there are updates for your graphics drivers https://support.mozilla.org/en-US/kb/upgrade-graphics-drivers-use-hardware-acceleration