There is nothing wrong with your display. What you describe is normal for the Multiple Scan 1705 Display and typical of all entry level 17-in. displays.
When you display more white areas on your monitor, this draws more current causes the screen raster to move slightly. The same size display at a higher price point contains higher cost circuitry that compensates for the raster movement.
When using MacTest Pro test patterns (all white screen), the various Apple Displays all have different levels of raster movement, or high voltage regulation. This is normal on all displays, regardless of manufacturer.