万万没想到，写了快三年前端，有不会用的css，居然还有完全没听过、见过的css属性，而且还是CSS2的内容！
关于counter-reset、content-increment两个属性的详解可以参看张鑫旭的博文：《CSS计数器(序列数字字符自动递增)详解》，这里做个记录，写个demo
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>content-increment</title>
<style>
.test li {margin:16px 0;padding:0;list-style:none;}
.test li li:before{color:#f00;font-family:\'Microsoft YaHei\';}
.counter1 li{counter-increment:testname;}
.counter1 li:before{content:counter(testname)".";}
.counter2 li{counter-increment:testname2 2;}
.counter2 li:before{content:counter(testname2)"/";}
.counter3 li{counter-increment:testname3 -1;}
.counter3 li:before{content:counter(testname3)")";}
.counter4 li{counter-increment:testname4;}
.counter4 li:before{content:counter(testname4, upper-roman)". ";}
.counter5 {counter-reset:testname5;}
.counter5 li:before{content: counters(testname5, \'-\') \'. \'; counter-increment: testname5;color:blue;font-family: \'Microsoft YaHei\';}
</style>
</head>
<body>
<ul class="test">
<li class="counter1">
<strong>默认时的计数器：</strong>
<ul>
<li>列表项</li>
<li>列表项</li>
<li>列表项</li>
</ul>
</li>
<li class="counter2">
<strong>修改计数器每次增加的值为2：</strong>
<ul>
<li>列表项</li>
<li>列表项</li>
<li>列表项</li>
</ul>
</li>
<li class="counter3">
<strong>修改计数器每次增加的值为-1：</strong>
<ul>
<li>列表项</li>
<li>列表项</li>
<li>列表项</li>
</ul>
</li>
<li class="counter4">
<strong>修改计数器以罗马字符显示：</strong>
<ul>
<li>列表项</li>
<li>列表项</li>
<li>列表项</li>
</ul>
</li>
</ul>
<ul class="test counter5">
<strong>计数器以嵌套计数显示:</strong>
<li>父级</li>
<li>父级
<ul class="counter5">
<li>子级1</li>
<li>子级2</li>
<li>子级3</li>
</ul>
</li>
<li>父级
<ul class="counter5">
<li>子级1</li>
<li>子级2</li>
<li>子级3</li>
</ul>
</li>
<li>父级</li>
</ul>
</body>
</html>
兼容情况还不错：