用CSS制作的很不错的简洁的网页导航下拉菜单

　　用CSS和javascript制作的非常简洁的网页导航菜单，而且还具有下拉的功能啊！呵呵

<style type="text/css">
/*Credits: Dynamic Drive CSS Library */
/*URL: <a href="http://www.dynamicdrive.com/style/" target="_blank">http://www.dynamicdrive.com/style/</a> */
.suckertreemenu ul{
margin: 0;
padding: 0;
list-style-type: none;
}
/*Top level list items*/
.suckertreemenu ul li{
position: relative;
display: inline;
float: left;
background-color: #F3F3F3; /*overall menu background color*/
}
/*Top level menu link items style*/
.suckertreemenu ul li a{
display: block;
width: 90px; /*Width of top level menu link items*/
padding: 1px 8px;
border: 1px solid black;
border-left-width: 0;
text-decoration: none;
color: navy;
}
/*1st sub level menu*/
.suckertreemenu ul li ul{
left: 0;
position: absolute;
top: 1em; /* no need to change, as true value set by script */
display: block;
visibility: hidden;
}
/*Sub level menu list items (undo style from Top level List Items)*/
.suckertreemenu ul li ul li{
display: list-item;
float: none;
}
/*All subsequent sub menu levels offset after 1st level sub menu */
.suckertreemenu ul li ul li ul{
left: 159px; /* no need to change, as true value set by script */
top: 0;
}
/* Sub level menu links style */
.suckertreemenu ul li ul li a{
display: block;
width: 160px; /*width of sub menu levels*/
color: navy;
text-decoration: none;
padding: 1px 5px;
border: 1px solid #ccc;
}
.suckertreemenu ul li a:hover{
background-color: black;
color: white;
}
/*Background image for top level menu list links */
.suckertreemenu .mainfoldericon{
background: #F3F3F3 url(media/arrow-down.gif) no-repeat center right;
}
/*Background image for subsequent level menu list links */
.suckertreemenu .subfoldericon{
background: #F3F3F3 url(media/arrow-right.gif) no-repeat center right;
}
* html p#iepara{ /*For a paragraph (if any) that immediately follows suckertree menu, add 1em top spacing between the two in IE*/
padding-top: 1em;
}
/* Holly Hack for IE */
* html .suckertreemenu ul li { float: left; height: 1%; }
* html .suckertreemenu ul li a { height: 1%; }
/* End */
</style>
<script type="text/javascript">
//SuckerTree Horizontal Menu (Sept 14th, 06)
//By Dynamic Drive: <a href="http://www.dynamicdrive.com/style/" target="_blank">http://www.dynamicdrive.com/style/</a>
var menuids=["treemenu1"] //Enter id(s) of SuckerTree UL menus, separated by commas
function buildsubmenus_horizontal(){
for (var i=0; i<menuids.length; i++){
　var ultags=document.getElementById(menuids[i]).getElementsByTagName("ul")
　　for (var t=0; t<ultags.length; t++){
　if (ultags[t].parentNode.parentNode.id==menuids[i]){ //if this is a first level submenu
　ultags[t].style.top=ultags[t].parentNode.offsetHeight+"px" //dynamically position first level submenus to be height of main menu item
　ultags[t].parentNode.getElementsByTagName("a")[0].className="mainfoldericon"
　}
　else{ //else if this is a sub level menu (ul)
　　ultags[t].style.left=ultags[t-1].getElementsByTagName("a")[0].offsetWidth+"px" //position menu to the right of menu item that activated it
　　ultags[t].parentNode.getElementsByTagName("a")[0].className="subfoldericon"
　}
　　ultags[t].parentNode.onmouseover=function(){
　　this.getElementsByTagName("ul")[0].style.visibility="visible"
　　}
　　ultags[t].parentNode.onmouseout=function(){
　　this.getElementsByTagName("ul")[0].style.visibility="hidden"
　　}
　　}
　}
}
if (window.addEventListener)
window.addEventListener("load", buildsubmenus_horizontal, false)
else if (window.attachEvent)
window.attachEvent("onload", buildsubmenus_horizontal)
</script>
<div class="suckertreemenu">
<ul id="treemenu1">
<li><a href="#" style="border-left: 1px solid black">Item 1</a></li>
<li><a href="#">Item 2</a></li>
<li><a href="#">Folder 1</a>
　<ul>
　<li><a href="#">Sub Item 1.1</a></li>
　<li><a href="#">Sub Item 1.2</a></li>
　<li><a href="#">Sub Item 1.3</a></li>
　<li><a href="#">Sub Item 1.4</a></li>
　</ul>
</li>
<li><a href="#">Item 3</a></li>
<li><a href="#">Folder 2</a>
　<ul>
　<li><a href="#">Sub Item 2.1</a></li>
　<li><a href="#">Folder 2.1</a>
　　<ul>
　　<li><a href="#">Sub Item 2.1.1</a></li>
　　<li><a href="#">Sub Item 2.1.2</a></li>
　　<li><a href="#">Sub Item 2.1.3</a></li>
　　<li><a href="#">Sub Item 2.1.4</a></li>
　　</ul>
　</li>
</ul>
</a>
</li>
<li><a href="#">Item 4</a></li>
</ul>
<br style="clear: left;" />
</div>
<p id="iepara">Rest of content here</p>