简洁实用js下拉菜单代码

<ul id="sddm">
<li><a href="#"
 onmouseover="mopen('m1')"
 onmouseout="mclosetime()">Home</a>
 <div id="m1"
     onmouseover="mcancelclosetime()"
     onmouseout="mclosetime()">
 <a href="#">HTML Drop Down</a>
 <a href="#">DHTML Menu</a>
 <a href="#">javascript DropDown</a>
 <a href="#">Cascading Menu</a>
 <a href="#">CSS Horizontal Menu</a>
 </div>
</li>
<li><a href="#"
 onmouseover="mopen('m2')"
 onmouseout="mclosetime()">Download</a>
 <div id="m2"
     onmouseover="mcancelclosetime()"
     onmouseout="mclosetime()">
 <a href="#">ASP Dropdown</a>
 <a href="#">Pulldown menu</a>
 <a href="#">AJAX Drop Submenu</a>
 <a href="#">DIV Cascading Menu</a>
 </div>
</li>
<li><a href="#">Order</a></li>
<li><a href="#">Help</a></li>
<li><a href="http://www.yuju100.com">语句百分网</a></li>
</ul>
<div style="clear:both"></div>

#sddm
{
margin: 0;
 padding: 0;
 z-index: 30}

#sddm li
{ margin: 0;
 padding: 0;
 list-style: none;
 float: left;
 font: bold 11px arial}

#sddm li a
{ display: block;
 margin: 0 1px 0 0;
 padding: 4px 10px;
 width: 60px;
 background: #5970B2;
 color: #FFF;
 text-align: center;
 text-decoration: none}

#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: 11px arial}

 #sddm div a:hover
 { background: #49A3FF;
  color: #FFF}

var timeout = 500;
var closetimer = 0;
var ddmenuitem = 0;

// open hidden layer
function mopen(id)
{
 // cancel close timer
 mcancelclosetime();

 // close old layer
 if(ddmenuitem) ddmenuitem.style.visibility = 'hidden';

 // get new layer and show it
 ddmenuitem = document.getElementById(id);
 ddmenuitem.style.visibility = 'visible';

}
// close showed layer
function mclose()
{
 if(ddmenuitem) ddmenuitem.style.visibility = 'hidden';
}

// go close timer
function mclosetime()
{
 closetimer = window.setTimeout(mclose, timeout);
}

// cancel close timer
function mcancelclosetime()
{
 if(closetimer)
 {
  window.clearTimeout(closetimer);
  closetimer = null;
 }
}

// close layer when click-out
document.onclick = mclose;