css
1.display
display:inline 将块元素显示为内联元素
display:block 内联元素显示为块元素
2.position
常常配合子绝（absolute）父相（relative）使用
sticky 基于用户的滚动位置来定位。
粘性定位的元素是依赖于用户的滚动，在 position:relative 与 position:fixed 定位之间切换。
3.float
元素浮动之后，周围的元素会重新排列，为了避免这种情况，使用 clear 属性。
clear:both
4.导航栏
4.1ul li a:not(.active) {background-color: #ddd;}
以上css实现了除了选中标签外的其他标签的背景颜色设置为灰色
4.2ul li a:hover:not(.active) {background-color: #ddd;}
以上css是实现了当鼠标移动到某个元素上时，当这个元素不是被选中的元素时就置灰
4.3垂直导航栏
<style>
body {
margin: 0;
}
ul {
list-style-type: none;
margin: 0;
padding: 0;
width: 25%;
background-color: #f1f1f1;
position: fixed;
height: 100%;
overflow: auto;
}
li a {
display: block;
color: #000;
padding: 8px 16px;
text-decoration: none;
}
li a.active {
background-color: #4CAF50;
color: white;
}
li a:hover:not(.active) {
background-color: #555;
color: white;
}
</style>
</head>
<body>
<ul>
<li><a class="active" href="#home">主页</a></li>
<li><a href="#news">新闻</a></li>
<li><a href="#contact">联系</a></li>
<li><a href="#about">关于</a></li>
</ul>
<div style="margin-left:25%;padding:1px 16px;height:1000px;">
<h2>Fixed Full-height Side Nav</h2>
<h3>Try to scroll this area, and see how the sidenav sticks to the page</h3>
<p>Notice that this div element has a left margin of 25%. This is because the side navigation is set to 25% width. If you remove the margin, the sidenav will overlay/sit on top of this div.</p>
<p>Also notice that we have set overflow:auto to sidenav. This will add a scrollbar when the sidenav is too long (for example if it has over 50 links inside of it).</p>
<p>Some text..</p>
<p>Some text..</p>
<p>Some text..</p>
<p>Some text..</p>
<p>Some text..</p>
<p>Some text..</p>
<p>Some text..</p>
</div>
</body>
4.4水平导航栏
<style>
body {margin:0;}
ul {
list-style-type: none;
margin: 0;
padding: 0;
overflow: hidden;
background-color: #333;
position: fixed;
top: 0;
width: 100%;
}
li {
float: left;
}
li a {
display: block;
color: white;
text-align: center;
padding: 14px 16px;
text-decoration: none;
}
li a:hover:not(.active) {
background-color: #111;
}
.active {
background-color: #4CAF50;
}
</style>
</head>
<body>
<ul>
<li><a class="active" href="#home">主页</a></li>
<li><a href="#news">新闻</a></li>
<li><a href="#contact">联系</a></li>
<li><a href="#about">关于</a></li>
</ul>
<div style="padding:20px;margin-top:30px;background-color:#1abc9c;height:1500px;">
<h1>Fixed Top Navigation Bar</h1>
<h2>Scroll this page to see the effect</h2>
<h2>The navigation bar will stay at the top of the page while scrolling</h2>
<p>Some text some text some text some text..</p>
<p>Some text some text some text some text..</p>
<p>Some text some text some text some text..</p>
<p>Some text some text some text some text..</p>
<p>Some text some text some text some text..</p>
<p>Some text some text some text some text..</p>
<p>Some text some text some text some text..</p>
<p>Some text some text some text some text..</p>
<p>Some text some text some text some text..</p>
<p>Some text some text some text some text..</p>
<p>Some text some text some text some text..</p>
<p>Some text some text some text some text..</p>
<p>Some text some text some text some text..</p>
<p>Some text some text some text some text..</p>
<p>Some text some text some text some text..</p>
<p>Some text some text some text some text..</p>
<p>Some text some text some text some text..</p>
<p>Some text some text some text some text..</p>
<p>Some text some text some text some text..</p>
<p>Some text some text some text some text..</p>
</div>
</body>
5.下拉菜单
5.1
<style>
.dropbtn {
background-color: #4CAF50;
color: white;
padding: 16px;
font-size: 16px;
border: none;
cursor: pointer;
}
.dropdown {
position: relative;
display: inline-block;
}
.dropdown-content {
display: none;
position: absolute;
background-color: #f9f9f9;
min-width: 160px;
box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
}
.dropdown-content a {
color: black;
padding: 12px 16px;
text-decoration: none;
display: block;
}
.dropdown-content a:hover {background-color: #f1f1f1}
.dropdown:hover .dropdown-content {
display: block;
}
.dropdown:hover .dropbtn {
background-color: #3e8e41;
}
</style>
</head>
<body>
<h2>下拉菜单</h2>
<p>鼠标移动到按钮上打开下拉菜单。</p>
<div class="dropdown">
<button class="dropbtn">下拉菜单</button>
<div class="dropdown-content">
<a href="http://www.runoob.com">菜鸟教程 1</a>
<a href="http://www.runoob.com">菜鸟教程 2</a>
<a href="http://www.runoob.com">菜鸟教程 3</a>
</div>
</div>
</body>
6.表单
6.1 label和input一起使用，当用户选择label标签时，浏览器会自动将焦点转移到个label相关的input上
通过为input设置属性id，在label标签中设置for=id使label文本与对应的inpu他结合起来。
即label的for属性要与input的id属性一致
6.2
<style>
input[type=text], select {
width: 100%;
padding: 12px 20px;
margin: 8px 0;
display: inline-block;
border: 1px solid #ccc;
border-radius: 4px;
box-sizing: border-box;
}
input[type=submit] {
width: 100%;
background-color: #4CAF50;
color: white;
padding: 14px 20px;
margin: 8px 0;
border: none;
border-radius: 4px;
cursor: pointer;
}
input[type=submit]:hover {
background-color: #45a049;
}
div {
border-radius: 5px;
background-color: #f2f2f2;
padding: 20px;
}
</style>
<body>
<div>
<form action="/action_page.php">
<label for="fname">First Name</label>
<input type="text" id="fname" name="firstname" placeholder="Your name..">
<label for="lname">Last Name</label>
<input type="text" id="lname" name="lastname" placeholder="Your last name..">
<label for="country">Country</label>
<select id="country" name="country">
<option value="australia">Australia</option>
<option value="canada">Canada</option>
<option value="usa">USA</option>
</select>
<input type="submit" value="Submit">
</form>
</div>
</body>
7.网页布局
7.1 加了box-sizing:border-box属性，padding和border的值就不会在影响元素的宽高，相当于把padding和border的值都算在content里
7.2 overflow:hidden最直白的作用就是当元素内的内容溢出的时候使它隐藏溢出的部分
7.3
<style>
* {
box-sizing: border-box;
}
body {
font-family: Arial;
padding: 10px;
background: #f1f1f1;
}
/* 头部标题 */
.header {
padding: 30px;
text-align: center;
background: white;
}
.header h1 {
font-size: 50px;
}
/* 导航条 */
.topnav {
overflow: hidden;
background-color: #333;
}
/* 导航条链接 */
.topnav a {
float: left;
display: block;
color: #f2f2f2;
text-align: center;
padding: 14px 16px;
text-decoration: none;
}
/* 链接颜色修改 */
.topnav a:hover {
background-color: #ddd;
color: black;
}
/* 创建两列 */
/* Left column */
.leftcolumn {
float: left;
width: 75%;
}
/* 右侧栏 */
.rightcolumn {
float: left;
width: 25%;
background-color: #f1f1f1;
padding-left: 20px;
}
/* 图像部分 */
.fakeimg {
background-color: #aaa;
width: 100%;
padding: 20px;
}
/* 文章卡片效果 */
.card {
background-color: white;
padding: 20px;
margin-top: 20px;
}
/* 列后面清除浮动 */
.row:after {
content: "";
display: table;
clear: both;
}
/* 底部 */
.footer {
padding: 20px;
text-align: center;
background: #ddd;
margin-top: 20px;
}
/* 响应式布局 - 屏幕尺寸小于 800px 时，两列布局改为上下布局 */
@media screen and (max-width: 800px) {
.leftcolumn, .rightcolumn {
width: 100%;
padding: 0;
}
}
/* 响应式布局 -屏幕尺寸小于 400px 时，导航等布局改为上下布局 */
@media screen and (max-width: 400px) {
.topnav a {
float: none;
width: 100%;
}
}
</style>
</head>
<body>
<div class="header">
<h1>我的网页</h1>
<p>重置浏览器大小查看效果。</p>
</div>
<div class="topnav">
<a href="#">链接</a>
<a href="#">链接</a>
<a href="#">链接</a>
<a href="#" style="float:right">链接</a>
</div>
<div class="row">
<div class="leftcolumn">
<div class="card">
<h2>文章标题</h2>
<h5>2019 年 4 月 17日</h5>
<div class="fakeimg" style="height:200px;">图片</div>
<p>一些文本...</p>
<p>菜鸟教程 - 学的不仅是技术，更是梦想！菜鸟教程 - 学的不仅是技术，更是梦想！菜鸟教程 - 学的不仅是技术，更是梦想！菜鸟教程 - 学的不仅是技术，更是梦想！</p>
</div>
<div class="card">
<h2>文章标题</h2>
<h5>2019 年 4 月 17日</h5>
<div class="fakeimg" style="height:200px;">图片</div>
<p>一些文本...</p>
<p>菜鸟教程 - 学的不仅是技术，更是梦想！菜鸟教程 - 学的不仅是技术，更是梦想！菜鸟教程 - 学的不仅是技术，更是梦想！菜鸟教程 - 学的不仅是技术，更是梦想！</p>
</div>
</div>
<div class="rightcolumn">
<div class="card">
<h2>关于我</h2>
<div class="fakeimg" style="height:100px;">图片</div>
<p>关于我的一些信息..</p>
</div>
<div class="card">
<h3>热门文章</h3>
<div class="fakeimg"><p>图片</p></div>
<div class="fakeimg"><p>图片</p></div>
<div class="fakeimg"><p>图片</p></div>
</div>
<div class="card">
<h3>关注我</h3>
<p>一些文本...</p>
</div>
</div>
</div>
<div class="footer">
<h2>底部区域</h2>
</div>
</body>
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