1.vh是相对于浏览器视口的高度定位大小 视口大小为100,1vh=1/100;
2.vw是相对于浏览器视口的宽度定位大小 视口大小为100,1vw=1/100;
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<style>
.box1{
width:100vw;
height:30vh;
background:cadetblue;
margin-bottom:0.9em;
}
.box2{
width:100vw;
height:30vh;
background:red;
margin-bottom:0.8em;
}
.box3{
width:100vw;
height:30vh;
background:fuchsia;
}
</style>
<body>
<div class="box1"></div>
<div class="box2"></div>
<div class="box3"></div>
</body>
</html>