Properties for CSS Positioning

Property Values
top length | percentage | auto

top sets the position of the element's top edge. For absolutely positioned elements, this is relative to the HTML page's top edge. (The page's upper left corner is coordinate [0,0]). For relatively positioned elements, this is a positive or negative offset from the default position.

The position can be specified either by a length unit (such as 200px for 200 pixels) or as a percentage of the containing element's height (such as 50% for half the containing element's height).

auto specifies placement at the element's default location.