padding-left:10px //左边距10px
padding-top:10px //上边距10px
padding-right:10px //右边距10px
padding-bottom:10px //下边距10%，相对于⽗级元素的width
padding:10px 10px 10px 10% //等同于上⾯四⾏ 百分⽐是对应⽗标签的⼤⼩
padding:5px 10px //上下边距5px、左右边距10px
padding:5px 10px 20px //上边距 左右边距 下边距
padding:10px //上下左右边距10px
border-left:3px solid #000 //左边距10px dotted dashed
border-top:3px solid #000 //上边距10px
border-right:3px solid #000 //右边距10px
border-bottom:3px solid #000 //下边距10%，相对于⽗级元素的width
border:3px solid #000 //等同于上⾯四⾏
margin-left:10px //左边距10px
margin-top:10px //上边距10px
margin-right:10px //右边距10px
margin-bottom:10% //下边距10%，相对于⽗级元素的width
margin:10px 10px 10px 10% //等同于上⾯四⾏
margin:5px 10px //上下边距5px、左右边距10px
margin:10px //上下左右边距10px
boxWidth=contentWidth
box-sizing:border-box //声明
boxWidth=contentWidth+border+padding
上下两个兄弟盒⼦的margin都为正取⼤，都为负取⼩，⼀正⼀负相加
⽗⼦元素盒⼦的margin（假设没有内边距或边框把外边距分隔开），也会合并；只有普通⽂档流中块框的垂直外边距才会发⽣外边距合并。⾏内框、浮动框或绝对定位之间的外边距不会合并
⽗元素{
overflow:auto;
}
⽗元素::before{
display: table;
content: "";
}
<!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>
* {
margin: 0;
padding: 0;
}
.big {
width: 500px;
height: 500px;
background-color: red;
/* padding:10px */
}
.small {
width: 200px;
height: 200px;
background-color: blue;
border: 10px dashed #000
}
.box {
box-sizing: border-box;
width: 200px;
height: 200px;
background-color: green;
border: 5px solid #000;
padding: 10px
}
.top {
width: 100px;
height: 100px;
background-color: red;
margin-bottom: -10px;
}
.bottom {
width: 100px;
height: 100px;
background-color: blue;
margin-top: -10px
}
.father {
width: 200px;
height: 200px;
background-color: red;
}
.father::before {
display: table;
content: ''
}
.son {
width: 50px;
height: 50px;
background-color: blue;
margin-top: 20px
}
</style>
</head>
<body>
<!-- <div class="big">
<div class="small">
</div>
</div> -->
<!-- <br> -->
<!-- <div class="box">
</div> -->
<!-- <div class="top"></div>
<div class="bottom"></div> -->
<div class="father">
<div class="son"></div>
</div>
</body>
</html>
