选择器类型及盒模型

1、class的使用

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style>
        /*#p1{
            font-size: 30px;
            color: green;
        }
        #p2{
            color: green;
            text-decoration: underline;
        }
        #p3{
            font-size: 30px;
            text-decoration: underline;
        }*/

        .lg{
            font-size: 30px;
        }
        .lv{
            color: green;
        }
        .un{
            text-decoration: underline;
        }

    </style>
</head>
<body>
     <!-- 公共类 -->
     <p id="p1" class="lg lv">张孕康1</p>
     <p id="p2" class="lv un">张孕康2</p>
     <p id="p3" class="lg un">张孕康3</p>

    
</body>
</html>

2、后代选择器

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style>
        .father .wu{
            color: green;
        }

    </style>
</head>
<body>

    <div class="father">
        <p>alex</p>
        <ul>
            <li>
                <p class="wu">wusir</p>
            </li>
        </ul>
    </div>

    <p class="wu">日天</p>
    
</body>
</html>

3、子带选择器

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style>
        /*.father>p{
            color: red;
        }*/
        .father>ul>li{
            width: 100px;
        }
        .container{
            color: red;
        }
    </style>
</head>
<body>
    <div class="father">
        <p>alex</p>
        <p>alex</p>
        <p>alex</p>
        <p>alex</p>
        <div class="content">
            <p>wusir</p>
        </div>
        <ul>
            <li>
                alex2
                <ul>
                    <li>wusir</li>
                </ul>
            </li>
        </ul>
    </div>

    <div class="container">
        <p>日天</p>
    </div>

</body>
</html>

4、属性选择器

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title></title>
    <style>
        form input[type='text']{
            background-color: red;
        }
        form input[type='password']{
            background-color: yellow;
        }
        form #user{
            background-color: green;            
        }
    </style>
</head>
<body>
    
    <form action="">
        <input type="text" id="user">
        <input type="password">
    </form>
</body>
</html>

5、伪类选择器

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title></title>
    <style>
        /*a:hover{
            color: #ff6700
        }*/
        /*爱恨准则 LoVe HAte*/
        /*没有被访问的a标签的颜色*/
        a:link{
            color: green;
        }
        /*访问过后的a标签的颜色*/
        a:visited{
            color: yellow;
        }
        /*鼠标悬停的时候a标签的颜色*/
        a:hover{
            color: red;
        }

        a:active{
            color: blue;
        }
        span:hover{
            color: red;
            font-size: 24px;
            text-decoration: underline;
        }
        .child{
            display: none;
        }
        .father:hover .child{
            color: red;
            display: block;
        }

    </style>
</head>
<body>
    <a href="#">百度一下</a>

    <span>alex</span>

    <div class="father">
        wusir
        <p class="child">alex</p>
    </div>
    
</body>
</html>

6、伪元素选择器

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style>
        p:first-letter{
            color: red;
            font-size: 26px;
        }
        /*用伪元素 属性一定是content*/

        /*伪元素选择器与后面的布局有很大关系*/
        p:before{
            content: '$'
        }
        p:after{
            content: '.'
        }
        .box2{

            /*需求:这个盒子一定是块级标签  span==>块 并且不再页面中占位置。未来与布局有很大关系 */

            /*隐藏元素 不占位置*/
            /*display: none;*/
            display: block;
            
            /*display: none;*/
            /*隐藏元素 占位置*/
            visibility: hidden;
            height: 0;

        }

    </style>
</head>
<body>
    <p class="box">
        <span>alex</span>
    </p>

    <span class="box2">alex</span>
    <div>wusir</div>
    
</body>
</html>

7、盒模型

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style>
        .box{
            width: 200px;
            height: 200px;
            background-color: red;
            padding: 50px;
            border: 10px solid green;
            /*margin-left: 50px;*/
        }
    </style>
</head>
<body>
    <!-- 
    width:内容的宽度
    height:内容的高度
    padding:内边距
    border:边框
    margin:外边距
     -->
     <div class="box"></div>
    
</body>
</html>

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转载自www.cnblogs.com/P-Z-W/p/11260723.html