<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<!--内部样式-->
<style>
.demo a {
float: left;
display: block;
height: 50px;
width: 50px;
border-radius: 10px;
background: #bd7fff;
text-align: center;
color: #d502ff;
text-decoration: none;
/*margin向右偏移*/
margin-right: 5px;
font: bold 20px/50px Arial
}
/*属性名，属性名=属性值（正则）
= 绝对等于
*= 包含这个元素
^= 以这个元素开头
$= 以这个元素结尾
*/
/*存在id属性的元素 a[]{}*/
/*a[id]{*/
/* background: #d65f2f;*/
/*}*/
a[id = first]{
background: #35d62f;
}
a[href*="pdf"]{
background: #d6be37;
}
a[class = "links item first"]{
color: blue;
}
</style>
</head>
<body>
<p class="demo">
<a href="https://www.baidu.com" class="links item first" id="first">1</a>
<a href="" 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>
原文：https://www.cnblogs.com/saxonsong/p/14741482.html