<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style>
bodu{
margin: 0px;
}
.top{
width: calc(100% - 10px);
height: 50px;
margin: 5px;
background-color: red;
}
.menu{
float: left;
width: calc(20% - 10px);
height: 100px;
margin: 5px;
background-color: green;
}
.content{
float: left;
width: calc(80% - 10px);
height: 100px;
margin: 5px;
background-color: yellow;
}
.main{
clear: both;
}
</style>
</head>
<body>
<div class="top"></div>
<div class='main'>
<div class='menu'></div>
<div class='content'></div>
</div>
</body>
</html>