when  min-height  is set but  height  is not set,  height  and  min-height  of the child element will not take effect  height  or  min-height  of the 
 child element, based on whether the parent element has a fixed height or an effective percentage height 
.
 reference: 
  the percentage of height to min-height and the layout method of filling the screen  
 ide-parent-with-min-height-100-not-inheriting-height" rel= "nofollow noreferrer" Child inside parent with min-height:  
  min-height indicates the minimum height of the box, not the final height of the box. From the point of view of the outer box, it is understood that the outer final height is determined by the height of the inner elements of the box and the minimum height of the current box. 
 does not know its own height when the external box waits for the internal element to calculate the height, and the external height is unknown when the internal box height is set relative to the external box, so it is rendered according to its own content, and the final effect is that the height of the internal box has nothing to do with the outside. Under 
 
  mark, there is also this question 
 
  there may be the following questions 
 1 the IE, you use I remember IE8 or 6 does not support min-height 
 2 min-heihgt is set to a percentage? If you set the percentage to give the parent element a height 
 
  Congratulations on finding an ancient bug 
  https://bugs.webkit.org/show_.
ide-parent-with-min-height-100-not-inheriting-height" rel= "nofollow noreferrer" > https:/ / stackoverflow.com/que.  
 has not been fixed so far 
 
  min-height is the minimum height of this element you set. Because the size of the container in the browser may be enlarged by the contents in it, setting this property will ensure that your layout is correct, because it will not be less than the value you set 
 
  2019, and has not yet been fixed 
.