最常用的li导航写法：
#head_r_b {width:628px;height:60px;}
#head_r_b ul {list-style-type:none;height:44px;margin:0;padding:16px 0 0 20px;}
#head_r_b li {width:80px;height:44px;float:left;margin-right:2px;}
#head_r_b li a {width:80px;height:44px;background:url(images/over.jpg) no-repeat;float:left;font:bold 14px "宋体";color:#fff;text-align:center;line-height:50px;}
图片的li导航写法：
#top3 {
width:1002px;
height:85px;
}
#top3 ul {
list-style-type:none;padding:0;margin:0;
}
#top3 li {width:200px;height:85px;float:left;}
#top3 .tb1 a{width:200px;height:85px;background:url(images/nav1_1.jpg) left bottom no-repeat;float:left;font:bold 14px "宋体";color:#fff;text-align:center;line-height:50px;}
#top3 .tb1 a:hover {width:200px;height:85px;background:url(images/nav1_2.jpg) no-repeat;}#top3 .tb2 a{width:200px;height:85px;background:url(images/nav2_1.jpg) left bottom no-repeat;float:left;font:bold 14px "宋体";color:#fff;text-align:center;line-height:50px;}
#top3 .tb2 a:hover {width:200px;height:85px;background:url(images/nav2_2.jpg) no-repeat;}#top3 .tb3 a{width:200px;height:85px;background:url(images/nav3_2.jpg) left bottom no-repeat;float:left;font:bold 14px "宋体";color:#fff;text-align:center;line-height:50px;}
#top3 .tb3 a:hover {width:200px;height:85px;background:url(images/nav3_2.jpg) center bottom no-repeat;}#top3 .tb4 a{width:200px;height:85px;background:url(images/nav4_1.jpg) left bottom no-repeat;float:left;font:bold 14px "宋体";color:#fff;text-align:center;line-height:50px;}
#top3 .tb4 a:hover {width:200px;height:85px;background:url(images/nav4_2.jpg) no-repeat;}#top3 .tb5 a{width:200px;height:85px;background:url(images/nav5_1.jpg) left bottom no-repeat;float:left;font:bold 14px "宋体";color:#fff;text-align:center;line-height:50px;}
#top3 .tb5 a:hover {width:200px;height:85px;background:url(images/nav5_2.jpg) no-repeat;}个人写法仅限BLOG记载，只可意会，不可言传
