Three ways to center a CSS div

The first method margin method, the original code as shown in the figure.

#nei的margin的左右上下的边距. Get the center effect.

The second method. Pisition method, the location of the center is computed by absolute positioning, the code is as follows.

The third method. Span method, set a span that is not displayed in the page, set it to the height of the inline-box,span at the same time as the element to be centered, automatically extend to the height of parent 100%, and set two inline block elements to be centered vertically, so that the element can be centered. The specific code is as follows