双飞翼：因外形对称与鸟类的翅膀一样；
即两侧宽度固定中间宽度自适应;具体代码如下
<head>
<style>
.box{
width: 80%;
margin: auto;
}
.box1{
width: 100%;
background: hotpink;
float: left;
}
.box1-1{
height: 500px;
background: saddlebrown;
margin: 0px 200px;
}
.box2{
width: 150px;
height: 500px;
float: left;
margin-left: -100%;
background: red;
}
.box3{
width: 150px;
height: 500px;
float: right;
margin-left: -100%;
background: red;
}
</style>
</head>
<body>
<div class="box">
<div class="box1">
<div class="box1-1">
drhygwsery
</div>
</div>
<div class="box2">
</div>
<div class="box3">
</div>
</div>
</body>