<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>两列布局</title>
<style>
.left, .right {
height: 300px;
}
.left {
width: 300px;
background-color: #c9394a;
float: left;
}
.right {
background-color: #cccccc;
float: left;
}
</style>
</head>
<body>
<div class="left"></div>
<div class="right"></div>
</body>
</html>right不要设置float:left，设置浮动会脱离文档流，就不会继承父级宽度了，自然宽度是0
老师能解答下吗？