卖火柴的小舒
方法1：.parent {
width:800px;
height:500px;
border:2px solid #000;
position:relative;}
.child {
width:200px;
height:200px;
margin: auto;
position: absolute;
top: 0; left: 0; bottom: 0; right: 0;
background-color: red;}方法2：.parent { width:800px; height:500px; border:2px solid #000; display:table-cell; vertical-align:middle; text-align: center; } .child { width:200px; height:200px; display:inline-block; background-color: red; }方法3：.parent { width:800px; height:500px; border:2px solid #000; display:flex; justify-content:center; align-items:center; } .child { width:200px; height:200px; background-color: red; }方法4：.parent { width:800px; height:500px; border:2px solid #000; position:relative; } .child { width:300px; height:200px; margin:auto; position:absolute;/*设定水平和垂直偏移父元素的50%，再根据实际长度将子元素上左挪回一半大小*/ left:50%; top:50%; margin-left: -150px; margin-top:-100px; background-color: red; }