可以画个1/4之一的圆也可以画整个圆
<html>
<style type="text/css">
div{
background-color: #000;
width: 100px;
height: 100px;
border-radius: 50px;
position: absolute;
} #half{
background-color: #fff;
width: 50px;
height: 50px;
top: 1px;
left: 1px;
position: absolute;
border-radius: 50px 0 0 0 ;
}
</style>
<body>
<div>
<div id="half"></div> </div>
</body>
</html>
效果：
也可以画个半圆
<html>
<style type="text/css">
body{
background-color: #f00;
}
div{
content: "";
position: relative;
left: 200px;
width: 200px;
height: 400px;
border-radius: 0px 200px 200px 0px;
background-color: #fff;
display: block;
}
</style>
<body>
<div></div>
</body>
</html>