（2）找在线的css3手册
（3）如果是chm手册参考如下
http://jingyan.baidu.com/article/a948d65145f6ad0a2dcd2eae.html
li标签元素横排，关键是float属性，比如下例，li往左浮动，不清除浮动即可。居中显示，把ul，li用一个盒子nav装起来，并设置 “text-align: center”属性即可，即内容居中。具体如下例所示 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" " http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns=" http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/htmlcharset=gb2312" />
<title>无标题文档</title>
<style type="text/css">
#nav {
height: 30px
width: 100%
background-color: #c00
text-align: center
}
#nav ul {
margin: 0 0 0 30px
padding: 0px
font-size: 12px
color: #FFF
line-height: 30px
white-space: nowrap
}
#nav li {
list-style-type: none
display: inline
}
#nav li a {
text-decoration: none
font-family: Arial, Helvetica, sans-serif
padding: 7px 10px
color: #FFF
}
#nav li a:hover {
color: #ff0
background-color: #f00
}
</style>
</head><body>
<div id="nav">
<ul>
<li><a href=" http://www.52css.com/">HomePage</li></A>
<li><a href=" http://www.52css.com/">Div+CSS教程</a></li>
<li><a href=" http://www.52css.com/">CSS布局实例</a></li>
<li><a href=" http://www.52css.com/">CSS2.0教程 </a></li>
<li><a href=" http://www.52css.com/">CSS在线手册</a></li>
<li><a href=" http://www.52css.com/">Web标准</a></li>
<li><a href=" http://www.52css.com/">XHTML教程</a></li>
</ul>
</div></body>
</html>
