id + class 结合
标签[属性 符号 "值"]{
}
= ：绝对等于
*= ：包含
^= : 以什么开头
$= ：以什么结尾
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
.demo a{
float: left;
/*浮动*/
display: block;
height: 50px;
width: 50px;
border-radius: 10px;
background: #0000FF;
text-align: center;
color: gainsboro;
text-decoration: none;
margin-right:5px;
font:bold 20px/50px Arial;
}
/*id=first的元素*/
a[id="first"]{
background: yellow;
}
/*class=links的元素*/
a[class*="links"]{
background: green;
}
/*选中href中以http开头的元素*/
a[href^="http"]{
background: red;
}
/*选中href中以pdf结尾的元素*/
a[href$="pdf"]{
background: black;
}
</style>
</head>
<body>
<p class="demo">
<a href="http://www.baidu.com" class="links item first" id="first">1</a>
<a href="http://blog.kuangstudy.com" class="links item active" target="_blank" title="test">2</a>
<a href="images/123.html" class="links item">3</a>
<a href="images/123.png" class="links item">4</a>
<a href="images/123.jpg" class="links item">5</a>
<a href="abc" class="links item">6</a>
<a href="/a.pdf" class="links item">7</a>
<a href="/abc.pdf" class="links item">8</a>
<a href="abc.doc" class="links item">9</a>
<a href="abcd.doc" class="links item last">10</a>
</p>
</body>
</html>