html学习3-CSS补充

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position

fixed：把标签固定在页面的某处

例子：使用fixed制作“回到顶部”按钮

DOCTYPE html>
html lang="en">
head>
    meta charset="UTF-8">
    title>title>
head>
body>
    div onclick="GoTop();" style="width:50px;height:50px;background-color:black;color:white;
    position:fixed;bottom:20px;right:20px">
        返回顶部
    div>
    div style="height:5000px;background-color:#dddddd">
        ddfdfdadfdf
    div>
    script>
        function GoTop(){
            document.documentElement.scrollTop = 0;
            console.log(document.documentElement.scrollTop)
        }
    script>
body>
html>

例子2：固定页面头部

DOCTYPE html>
html lang="en">
head>
    meta charset="UTF-8">
    title>title>
    style>
        .pg-header{
            height:48px;
            background-color:black;
            color:#dddddd;
            position:fixed;
            top:0;
            right:0;
            left:0;
        }
        .pg-body{
            background-color:#dddddd;
            height:5000px;
            margin-top:50px;
        }
    style>
head>
body>
    div class="pg-header">头部div>
    div class="pg-body">内容div>
body>
html>

absolute：把标签固定在页面的某处，位置是绝对固定的

relative：通常和absolute一起用

例子：

DOCTYPE html>
html lang="en">
head>
    meta charset="UTF-8">
    title>title>
head>
body>
    div style="width:50px;height:50px;
    background-color:black;
    position:absolute;
    right:0;
    bottom:0;">

    div>
    div style="margin:0 auto;position:relative;width:500px;height:200px;border:1px solid red;">
        div style="position:absolute;left:0;bottom:0;width:50px;height:50px;background-color:black;">div>
    div>
    div style="margin:0 auto;position:relative;width:500px;height:200px;border:1px solid red;">
        div style="position:absolute;right:0;bottom:0;width:50px;height:50px;background-color:blue;">div>
    div>
    div style="margin:0 auto;position:relative;width:500px;height:200px;border:1px solid red;">
        div style="position:absolute;right:0;top:0;width:50px;height:50px;background-color:blue;">div>
    div>

    div style="height:5000px;background-color:#dddddd;">
        ddfdfdadfdf
    div>
body>
html>

页面分层显示：
z-index
opacity  透明 值：0-1

DOCTYPE html>
html lang="en">
head>
    meta charset="UTF-8">
    title>title>
head>
body>
    div style="display:none;z-index:10;
    position:fixed;background-color:white;
    height:100px;
    width:500px;
    top:50%;
    left:50%;
    margin-left:-250px;margin-top:-200px;

    ">
        input type="text">
        input type="text">
        input type="text">
    div>

    div style="display:none;z-index:9;position:fixed;background-color:#dddddd;
    top:0;
    bottom:0;
    left:0;
    right:0;
    opacity:0.5;
    ">div>

    div style="height:5000px;background-color:green;">
        ddfdfdadfdf
    div>
body>
html>

 
overflow
例子：

DOCTYPE html>
html lang="en">
head>
    meta charset="UTF-8">
    title>title>
head>
body>
    div style="height:200px;width:300px;overflow:hidden;">
        img src="IMG_1980.JPG">
    div>
    p>p>
    div style="height:200px;width:300px;overflow:auto;">
        img src="IMG_1980.JPG">
    div>
body>
html>

 
hover 
鼠标移动到标签时，属性才生效

DOCTYPE html>
html lang="en">
head>
    meta charset="UTF-8">
    title>title>
    style>
        .pg-header{
            position:fixed;
            right:0;
            left:0;
            top:0;
            height:48px;
            background-color:#2459a2;
            line-height:48px;
            }

        .pg-body{
            margin-top:50px;
            }

        .w{
            width:980px;
            margin:0 auto;
            }

        .pg-header .menu{
            display:inline-block;
            padding:0 10px 0 10px;
            color:white;
            }

        .pg-header .menu:hover{
            background-color:blue;
            }
    style>
head>
body>
    div class="pg-header">
        div class="w">
            a class="logo">LOGOa>
            a class="menu">全部a>
            a class="menu">42区a>
            a class="menu">段子a>
            a class="menu">1024a>
        div>
    div>
    div class="pg-body">
        div class="w">gdiv>
    div>
body>
html>

 
background-color　　背景颜色
background-image:url(‘xxx.gif‘)#默认。div大，图片重复放  
background-repeat:no-repeat/repeat-x/repeat-y 图片重复加载
background-position:10px 10px/position-x/position-y 移动背景图片

DOCTYPE html>
html lang="en">
head>
    meta charset="UTF-8">
    title>title>
head>
body>
    span style="background-image:url(‘微笑.gif‘);height:20px;width:20px;display:inline-block;">span>
    div style="height:35px;width:400px;position:relative;">
        input type="text" style="height:35px;width:370px;padding-right:30px" />
        span style="position:absolute;right:0;top:10px;background-image:url(‘微笑.gif‘);height:25px;width:25px;display:inline-block;">span>

    div>

    div style="width:200px;height:200px;border:1px solid red;
     background-image:url(‘土拨鼠.gif‘);
     background-repeat:no-repeat;
     background-position-x:10px;
     background-position-y:10px">div>
body>
html>

 
 
结束
html学习3-CSS补充
标签：分层   默认   func   type   hit   set   har   背景颜色   ext   
原文地址：https://www.cnblogs.com/goldtree358/p/12366679.html