<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
*{
margin: 0;
padding: 0;
}
.outer{
width:100%;
}
.left{
float: left;
width:200px;
height: 500px;
font-weight:bold;">orange;
}
.main{
float: left;
width:calc(100% - 200px);
height: 500px;
font-weight:bold;">yellowgreen;
}
</style>
</head>
<body>
<div class="outer">
<div class="left">左侧</div>
<div class="main">中间</div>
</div>
</body>
</html>
原文：https://www.cnblogs.com/eric-share/p/13733116.html