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Correction status：qualified
Teacher's comments：代码写的还行, 初学总是从模仿开始的
Collection
Collection
一、CSS相邻选择器
‘+’选择器则表示某元素后相邻的兄弟元素，也就是紧挨着的，是单个的
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<title></title>
<meta name="description" content="">
<meta name="viewport" content="width=device-width, initial-scale=1">
<style>
div+p{
background-color: aqua;
}
</style>
</head>
<body>
<div>
<p>第零个段落</p>
<div>
<p>第一个段落</p>
</div>
</div>
<p>第二个段落</p>
<p>第三个段落</p>
<p>第四个段落</p>
</body>
</html>二、CSS兄弟选择器
‘~’选择器则表示某元素后所有同级的指定元素，强调所有的
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Document</title>
<style> .h3 ~ p{ color: red; } </style>
</head>
<body>
<p>这是段落标签</p>
<p>这是段落标签</p>
<p>这是段落标签</p>
<h3>这是标题标签</h3>
<p>这是段落标签</p>
<p>这是段落标签</p>
<p>这是段落标签</p>
<h3>这是标题标签</h3>
<p>这是段落标签</p>
<p>这是段落标签</p>
<p>这是段落标签</p>
</body>
</html>三、CSS :nth-child() 选择器
:nth-child(n) 选择器匹配属于其父元素的第 N 个子元素，不论元素的类型。
<!DOCTYPE html>
<html>
<head>
<style>
p:nth-child(2){ background:#ff0000; }
</style>
</head>
<body>
<h1>这是标题</h1>
<p>第一个段落。</p>
<p>第二个段落。</p>
<p>第三个段落。</p>
<p>第四个段落。</p>
<p><b>注释：</b>Internet Explorer 不支持 :nth-child() 选择器。</p>
</body>
</html>四、CSS :nth-of-type() 选择器
:nth-of-type(n)选择器匹配同类型中的第n个同级兄弟元素。（n可以是一个数字，一个关键字，或者一个公式。）
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>菜鸟教程(runoob.com)</title>
<style>
p:nth-of-type(2)
{
background:#ff0000;
}
</style>
</head>
<body>
<h1>This is a heading</h1>
<p>The first paragraph.</p>
<p>The second paragraph.</p>
<p>The third paragraph.</p>
<p>The fourth paragraph.</p>
</body>
</html>五，padding对盒子宽度的影响
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<style type="text/css">
.box{
width: 200px;
height: 200px;
border: 1px solid #ddd;
}
.box2{
width: 200px;
height: 100px;
padding: 12px;
background: rgba(0,0,0,0.5);
color: #fff;
}
</style>
</head>
<body>
<div class="box">
<div class="box2">
设置了padding，会在原有的宽度上撑大
</div>
</div>
</body>
</html>解决方法：
1，减去padding值
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<style type="text/css">
.box{
width: 200px;
height: 200px;
border: 1px solid #ddd;
}
.box2{
width: 170px;
height: 100px;
padding: 15px;
background: rgba(0,0,0,0.5);
color: #fff;
}
</style>
</head>
<body>
<div class="box">
<div class="box2">
设置宽度时减去padding值
</div>
</div>
</body>
</html>
2，使用 box-sizing
box-sizing: content-box;看着不就是W3C的标准盒模型的计算方式（盒子宽度=宽度+padding+margin+border）
box-sizing: border-box;就是IE盒模型的计算方式（盒子宽度=padding+margin）
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<style type="text/css">
.box{
width: 200px;
height: 200px;
border: 1px solid #ddd;
}
.box2{
width: 200px;
height: 100px;
padding: 15px;
background: rgba(0,0,0,0.5);
color: #fff;
box-sizing: border-box;
}
</style>
</head>
<body>
<div class="box">
<div class="box2">
设置了 box-sizing: border-box; 宽度不用重新计算
</div>
</div>
</body>
</html>六、 margin中的同级塌陷, 嵌套传递与自动挤压
同级塌陷：同级元素设置了对各自设置了margin距离，谁小塌陷到大的里面
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<style>
.box1 {
width: 100px;
height: 100px;
background-color: lightblue;
margin-bottom: 10px;
}
.box2 {
width: 100px;
height: 100px;
background-color: lightcoral;
margin-top: 30px;
}
</style>
</head>
<body>
<div class="box1"></div>
<div class="box2"></div>
</body>
</html>
嵌套传递：给盒子内的元素设置margin，最后作用只会到外层的盒子，盒子内部之间设置间距需要用padding
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<style>
.box3 {
width: 200px;
height: 200px;
background-color: lightblue;
}
.box4 {
width: 100px;
height: 100px;
background-color: lightcoral;
margin-top: 50px;
}
</style>
</head>
<body>
<div class="box3">
<div class="box4"></div>
</div>
</body>
自动挤压：通过设置auto值实现居中显示
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<style>
.box3 {
width: 200px;
height: 200px;
background-color: lightblue;
margin: 0 auto;
}
</style>
</head>
<body>
<div class="box3">
</div>
</body>