100％高度使用顶部：0; left：0; bottom：0; right：0;

You can make 100% width and 100% height using top: 0; left: 0; bottom: 0; right: 0;

例如：你有一个div没有固定宽度&该div的高度。在这种情况下，你可以应用这种风格，使100％宽度&

Example: You have one div there is no fixed width & height for that div. in this case you can apply this style and make 100% width & height.

div{
 position: absolute;
 top: 0;
 right: 0;
 bottom: 0;
 left: 0;
}

JSFIDDLE DEMO

JSFIDDLE DEMO