CSS Pocket Reference, 3rd Edition

Types of Positioning

Static positioning

The element’s box is generated as normal. Block-level elements generate a rectangular box that is part of the document’s flow, and inline-level boxes generate one or more line boxes that flow within their parent element.

Relative positioning

The element’s box is offset by some distance. Its containing block can be considered to be the area that the element would occupy if it were not positioned. The element retains the shape it would have had were it not positioned, and the space that the element would ordinarily have occupied is preserved.

Absolute positioning

The element’s box is completely removed from the flow of the document and positioned with respect to its containing block, which may be another element in the document or the initial containing block (described in the next section). Whatever space the element might have occupied in the normal document flow is closed up, as though the element did not exist. The positioned element generates a block box, regardless of the type of box it would generate if it were in the normal flow.

Fixed positioning

The element’s box behaves as though it were set to absolute, but its containing block is the viewport itself.