Parent spreader achieve high internal width div elements:
父div添加属性:overflow:hidden;
When the child element positioning, not distraction parent element, because the child element has been out of the text flow
Arbitrary vertical and horizontal centering element method (single centrally Similarly):
position:absolute;
left:50%;
top:50%;
transform:translate(-50%,-50%); 移动元素自身高宽的一半，因为定位时元素有自身高宽
Vertical center vertica-align: middle, is applied to the sub-element row element in the parent element plus font-size: 0px and line-height: ...; achieve precise centering, or there will be a deviation
非图片在父元素上设置vertical-align:center;
图片在自身上设置vertical-align:center;
text-align: center; applies to a sub-element row element
Vertically centered way: by using the reference line elements of line
to be centered image after adding text, the parent element set high and the parent element row same high, then set font-size: 0px, can achieve image centered vertically
