1. The natural layout without any modify automatic layout is on the left. 2. A fluid layout described above float: left. 3. The location layout relative orientation and absolute orientation is relative to the parent div tags. Relative -- -- -- -- -- - to the elements should have in place for absolute reference point – – With parent div tag origin (top left) as the reference point. Because the outer layer is the position: relative, so layer is absolute, the outside layer in the upper left corner will be aligned for the displacement of the reference. Outer, of course, just write the position: relative, write down the left, top, these two values and are said to: with the elements should have in place for the layout of the reference to the origin of the left and top alignment. There is also a situation is, it's just a position: absolute; Outer no position: relative, then will find the point as a reference? At that time the principle is: if a parent element with relative, to a parent element as reference origin, if there is no position: relative to the reference origin is the body. If the position: absolute outer layer there is no relative, the two layout is no different. The last case, of course, is that the outer is: position: absolute; What is inside the position: relative, who would it be? According to the original principle, absolute origin will reference the body for layout, relative to reference he ought to have for layout in the location of origin, this time is actually refer to the outer layer on the upper left corner to layout the origin. Other depends on actual situation.

This concludes the body part