Study the position attribute of CSS again

Position: absoulte jumps out of the Document Stream. This attribute can be activated only when any trbl attribute of an element is set.
If this attribute is not set for the parent element, the offset of the element is relative to the entire screen. If it is set, it is relative to the parent element.
Fixed if the parent element does not set this attribute, the offset of the element is relative to the entire screen. If it is set, it is relative to the parent element.
Difference: fixed will be fixed.
Relative: the stream position of the document is retained, which is offset to the original stream position.
Clear: the role of both. Make the element independent from the floating element. If this parameter is not added, the original file stream location is retained. After this parameter is added, a new row is added.
When there is a wrapped Div, add a <Div style = "clear both"> </div> to the element, then the element outside is opened. Otherwise, do not open it.