What do the CSS position values mean?

static Default. An element with position: static always has the position the normal flow of the page gives it (a static element ignores any top, bottom, left, or right declarations)

relative An element with position: relative moves an element relative to its normal position, so "left:20" adds 20 pixels to the element's LEFT position

absolute An element with position: absolute is positioned at the specified coordinates relative to its containing block. The element's position is specified with the "left", "top", "right", and "bottom" properties

fixed An element with position: fixed is positioned at the specified coordinates relative to the browser window. The element's position is specified with the "left", "top", "right", and "bottom" properties. The element remains at that position regardless of scrolling. Works in IE7 (strict mode)


http://www.w3schools.com/Css/pr_class_position.asp