Most designers support the lowest common denominator to avoid image dithering.
The advantage of this approach is that it keeps the colors looking as they were intended, and makes the images look smoother. Nevertheless, it sacrifices quality that site visitors equipped with better video systems could enjoy. The colorDepth property of the screen object reveals the user's color bit depth. This property is very helpful if you're interested in providing the most suitable image for the user's color resolution. The conditional statement in the script checks if the browser supports the screen object.