效果
<body> <div class="box"> <span></span> </div> </body>代码如下
<style>
.box {
position: relative;
margin: 100px auto;
100px;
height: 200px;
background: blue;
}
.box span {
position: absolute;
left: 80px;
top: -15px;
0;
height: 0;
border: 10px solid transparent;
border-bottom-color: blue;
}
</style>
<body>
<div class="box">
<span></span>
</div>
</body>