CSS背景使用，引入、尺寸、平铺、定位、多重背景
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<style type="text/css">
*{
margin: auto;
padding: 0;
}
#a1{
width: 100px;
height: 100px;
border: 1px solid red;
margin-top: 30px;
border-radius: 15px 20%;
box-shadow: 5px 10px;
}
#a2{
width: 300px;
height: 300px;
border: 1px solid red;
background-image: url(../img/1.jpg);
background-size: 100% 100%;
background-repeat: no-repeat;
margin-top: 30px;
}
#a3{
width: 300px;
height: 300px;
border: 1px solid red;
background-image: url(../img/1.jpg);
background-position: bottom;
background-repeat: no-repeat;
margin-top: 30px;
}
#a4{
width: 400px;
height: 400px;
border: 1px solid red;
background-image: url(../img/1.jpg),url(../89ca0e54-6537-4aa4-8ac6-be6ec29b6636.jpg);
background-repeat: no-repeat;
margin-top: 30px;
}
</style>
</head>
<body>
<div id="a1">
</div>
<div id="a2">
</div>
<div id="a3">
</div>
<div id="a4">
</div>
</body>
</html>
