Margin collapse phenomenon (that is, the solution to set margin-top in the inner layer is invalid)

There are two div with nested relationship, if the padding value of the parent element of the outer div is 0, then the value of Margin-top or Margin-bottom of the inner Sub Div will be transferred to the outer parent Div, that is, the Magrin collapse phenomenon.

　　　　Workaround:

1. Add: Overflow:hidden on the parent element div;

2. Change the outer margin of the margin-top to the padding-top inner margin;

3. Parent Element Div produces margin overlapping edges with border that are not 0 padding or width not 0 and style is not none; the parent element adds padding-top:1px;

4. Let the parent element generate a block formating context, the following properties can be implemented
* Float:left/right
* Position:absolute
* Display:inline-block/table-cell (or other table type)
* Overflow:hidden/auto
Parent-level div plus: position:absolute;

Margin collapse phenomenon (that is, the solution to set margin-top in the inner layer is invalid)