Cascading Style Sheets: The Definitive Guide, Second Edition

Positioning

The idea behind positioning is fairly simple. It allows you to define exactly where element boxes will appear relative to where they would ordinarily be—or relative to a parent element, another element, or even to the browser window itself.

Basic Concepts

Before we delve into the various kinds of positioning, it’s a good idea to look at what types exist and how they differ. We’ll also need to define some basic ideas that are fundamental to understanding how positioning works.

Types of positioning

You can choose one of four different types of positioning, which affect how the element’s box is generated, by using the position property.

position

Values

static | relative | absolute | fixed | inherit

Initial value

static

Applies to

all elements

Inherited

no

Computed value

as specified

The values of position have the following meanings:

static

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 cause the creation of one or more line boxes that are flowed within their parent element.

relative

The element’s box is offset by some distance. 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

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 ...