Use the CSS rules for "child2" to see how absolute positioning removes an element from the flow and pins it to a pixel coordinate.
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Absolute positioning is usually used for artistic purposes. Such as overlapping objects for visual appeal. It is not however recommended to use for entire page layouts. Doing so will pin elements to pixel coordinates on the screen. Therefore on smaller screens your content will get cut off and not resize.
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CSS Positioning: Position absolute and relative explained by Kevin Powell [1]