.box {
/*width:占有宽度*/
width: 100%;
height: 200px;
background: #eee;
/*利用padding挤出1,3位置*/
padding: 0 200px;
/*内减盒模型*/
box-sizing: border-box;
position: relative;
}
.box p:first-child {
/*绝对定位*/
position: absolute;
width: 200px;
height: 200px;
background-color: green;
left: 0;
}
.box p:last-child {
/*绝对定位*/
position: absolute;
width: 200px;
height: 200px;
background-color: green;
right: 0;
top: 0;
}
.box p:nth-child(2) {
/*标准流 父盒子内容宽的比值*/
width: 100%;
height: 200px;
background-color: orange;
}
</style>
<body>
<div class="box">
<P></P>
<P></P>
<P></P>
</div>