PHP导航下拉菜单的实现

<style>
#sddm li a:hover
{ background: #49A3FF}
#sddm div
{ position: absolute;
visibility: hidden;
margin: 0;
padding: 0;
background: #EAEBD8;
border: 1px solid #5970B2}
#sddm div a
{ position: relative;
display: block;
margin: 0;
padding: 5px 10px;
width: auto;
white-space: nowrap;
text-align: left;
text-decoration: none;
background: #EAEBD8;
color: #2875DE;
font: 12px arial}
#sddm div a:hover
{ background: #49A3FF;
color: #FFF}
</style>
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<script type="text/javascript">
<!--
var timeout = 500;
var closetimer = 0;
var ddmenuitem = 0;
// open hidden layer
function mopen(id)
{
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ddmenuitem.style.visibility = 'visible';
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document.onclick = mclose;
// -->
</script>
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<div style="margin-top:5px;"> <a href="http://weibo.com/tcdd" target="_blank"><img src="images/top_pic02.jpg" /></a></div>
</span>
<ul class="nav"  id="sddm">
<li><a href="/">首页</a></li>
<li><a href="/plus/list.php?tid=1"   id="m1"   href="#">HTML DropDown</a>
<a href="#">DHTML DropDown menu</a>
<a href="#">JavaScript DropDown</a>
<a href="#">DropDown Menu</a>
<a href="#">CSS DropDown</a>
</div>
</li>
<li><a href="/plus/list.php?tid=2"   id="m2"   href="#">ASP Dropdown</a>
<a href="#">Pulldown menu</a>
<a href="#">AJAX dropdown</a>
<a href="#">DIV dropdown</a>
</div>
</li>
<li><a href="/plus/list.php?tid=3"   id="m3"   href="#">ASP Dropdown</a>
<a href="#">Pulldown menu</a>
<a href="#">AJAX dropdown</a>
<a href="#">DIV dropdown</a>
</div>
</li>
<li><a href="/plus/list.php?tid=4"   id="m4"   href="#">ASP Dropdown</a>
<a href="#">Pulldown menu</a>
<a href="#">AJAX dropdown</a>
<a href="#">DIV dropdown</a>
</div>
</li>
<li><a href="/plus/list.php?tid=5"   id="m5"   href="#">ASP Dropdown</a>
<a href="#">Pulldown menu</a>
<a href="#">AJAX dropdown</a>
<a href="#">DIV dropdown</a>
</div>
</li>
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<li><a href="/plus/list.php?tid=6"   id="m6"   href="#">ASP Dropdown</a>
<a href="#">Pulldown menu</a>
<a href="#">AJAX dropdown</a>
<a href="#">DIV dropdown</a>
</div>
</li>
<li><a href="/plus/list.php?tid=7"   id="m7"   href="#">ASP Dropdown</a>
<a href="#">Pulldown menu</a>
<a href="#">AJAX dropdown</a>
<a href="#">DIV dropdown</a>
</div>
</li>
</ul>
</dl>
</div>
</div>
</div>