给box添加一个边框
<html lang="EN">
<meta>
<head>
<meta charset="utf-8" />
<title>学习知识小结</title>
<style>
.box {
height:200px;
width:200px;
background-color:blue;
border:1px red solid;
}
</style>
</head>
<body>
<div class="box">盒子1</div>
</body>
</html><html lang="EN">
<meta>
<head>
<meta charset="utf-8" />
<title>学习知识小结</title>
<style>
.box {
height:200px;
width:200px;
background-color:blue;
border:1px red solid;
}
</style>
</head>
<body>
<div class="box">盒子1</div>
</body>
</html>