有四个属性：
static:静止
relative：相对的
fixed：固定的（广告等信息固定在网页的某个位置，不管你上下滑动位置不变）
absolu：绝对的
.box{
display:inline-block;
100px;
height: 100px;
background: blue;
color: rgb(71, 16, 16);
}
#two {
position: fixed;
top: 200px;
left: 100px;
background: red;
}
#one{
position: absolute;
top: 1000px;
left: 10px;
background: black;
}
#three{
position: sticky;
top: 200px;
left: 80px;
background: purple;
}
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<link rel="stylesheet" href="positionCSS.css">
</head>
<body>
<div class="box" id="one">one</div>
<div class="box" id="two">two</div>
<div class="box" id="three">three</div>
<div class="box" id="four">four</div>
</body>
</html>