CSS:background-position的用法

background-position的特殊用法：从一张图片中分离部分图片
<style>
ul { width:300px; height:300px; margin:0px auto; padding:0px; overflow:hidden; background:transparent url(image/menu_gray.jpg)}
li {list-style-type:none; width:100px; height:100px; float:left}
li a { display:block; width:100px; height:100px; text-decoration:none;
background:transparent url(image/menu_color.jpg) no-repeat 500px 500px; }
a#item1:hover {background-position: 0 0; }
a#item2:hover {background-position: -100px 0;}
a#item3:hover {background-position: -200px 0;}
a#item4:hover {background-position: 0 -100px;}
a#item5:hover {background-position: -100px -100px;}
a#item6:hover {background-position: -200px -100px;}
a#item7:hover {background-position: 0 -200px;}
a#item8:hover {background-position: -100px -200px;}
a#item9:hover {background-position: -200px -200px;}
</style>

<ul>
<li><a id="item1" href="#" title="Item 1">&nbsp;</a></li>
<li><a id="item2" href="#" title="Item 2">&nbsp;</a></li>
<li><a id="item3" href="#" title="Item 3">&nbsp;</a></li>
<li><a id="item4" href="#" title="Item 4">&nbsp;</a></li>
<li><a id="item5" href="#" title="Item 5">&nbsp;</a></li>
<li><a id="item6" href="#" title="Item 6">&nbsp;</a></li>
<li><a id="item7" href="#" title="Item 7">&nbsp;</a></li>
<li><a id="item8" href="#" title="Item 8">&nbsp;</a></li>
<li><a id="item9" href="#" title="Item 9">&nbsp;</a></li>
</ul>

所用到的图片
menu_gray.jpg

menu_color.jpg