<div></div>
html,body { /*这里没用*/
width: 100%;
height: 100%;
margin: 0;
padding: 0;
}
div {
width:0;
height:120px;
background-color: turquoise;
border: 120px solid transparent;
border-bottom: 120px solid white;
/*下面的只是垂直居中而已*/
margin: 0 auto;
position: relative;
top: 50%;
margin-top: -60px;
}