lovecoding
/
W250913


			
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							<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        /* 正常情况下 给一个元素加上padding 和 border 会导致元素的宽度和高度增加 */
        /* div{
            width: 200px;
            height: 200px;
            background-color: red;
            padding: 20px;
        } */

        div{
            width: 200px;
            height: 200px;
            background-color: red;
            padding: 20px;
            box-sizing: border-box;
        }


    </style>
</head>
<body>
    <div>hello world</div>
</body>
</html>