例子：
<html>
<head>
<style type="text/css">
ul.none{list-style-type:none}
ul.circle {list-style-type:circle}
ul.square {list-style-type:square}
ol.upper-roman {list-style-type:upper-roman}
ol.lower-alpha {list-style-type:lower-alpha}
</style>
</head>
<body>
<p>list-style-type none:</p>
<ul class="non
