Have 2 Monitors: if you have 2 of them, the Windows will be maximized over both screens. Check this value to use only the left screen.
Use fixed screenwidth: If you have 2 Monitors with different resolution, the width of Monitor 1 is calculated wrong.
In this case, add the resolution of Monitor 1 here manually.
Redraw screen after action: If you have 2 Monitors with different resolutions and use xcompmgr (Window-shadows), some Window-managers like oroborus do not redraw the screen correctly after resizing windows. If you check this point, an external program will redraw the screen with a different method.
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