In example H2, focus on the blue block (#box_2). Notice how I use only one offset, left: 100px;. This allows the #box_2 element to maintain its top edge and still shift 100 pixels to the left. If we applied a second offset to the top, we would see that our blue block (#box_2) is pulled to the top of the document. See that here, in example H3:

... and the fact that this paragraph is moved up proves the fact that the blue box is out of the document flow!

NOTE: Position absolute also removes the element from being a block level element, since it is totally out of the document flow.