弹出菜单

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>

<style>
*{ margin:0; padding:0; font-family:"微软雅黑"; font-size:18px;}
a{text-decoration:none;}

.popmenu { 400px; margin:50px auto;}

.popmenu ul { background:#B10000; height:25px; }
.popmenu ul li{float:left; 100px; position:relative;list-style:none;}

.popmenu ul li a{display:block;height:25px; line-height:25px;  text-align:center; color:white;}
.popmenu ul li a:hover{ background:#79951A; }

.popmenu ul li div{display:none; line-height:30px;100px; background:#528DF1; position:absolute;}
</style>

</head>

<body>
<div class="popmenu" id="popmenu">
    <ul>
        <li>
            <a class="first" href="#">菜单1</a>
            <div>
                <a href="http://www.baidu.com">吃饭</a>
                <a href="http://www.qq.com">睡觉</a>
                <a href="http://www.baidu.com">吃饭</a>
                <a href="http://www.qq.com">睡觉</a>  
                <a href="http://www.baidu.com">吃饭</a>
                <a href="http://www.qq.com">睡觉</a>
                <a href="http://www.baidu.com">吃饭</a>
                <a href="http://www.qq.com">睡觉</a>                           
            </div>
        </li>
        <li>
            <a href="#">菜单2</a>
            <div>
                <a href="http://www.baidu.com">吃饭</a>
                <a href="http://www.qq.com">睡觉</a>
                <a href="http://www.baidu.com">打豆豆</a>
            </div></li>
        <li><a href="#">菜单3</a><div>content3</div></li>                
        <li><a href="#">菜单4</a><div>content4</div></li>                
    </ul>
</div>

</body>
</html>
<script>

//获取firstchild
function firstChild(elem)
{
    var node = elem.firstChild ? elem.firstChild : null;
    while(node && node.nodeType != 1)
    {
        node = node.nextSibling;
    }
    return node;
}

//获取下一个同辈元素（ie下回忽略空白文节点）
function next(elem)
{
    var node = elem.nextSibling ? elem.nextSibling : null;
    while(node && node.nodeType != 1 )
    {
        node = node.nextSibling;
    }
    
    return node;
}

//获取上一个同辈元素（ie下回忽略空白文节点）
function prev(elem)
{
    var node = elem.previousSibling ? elem.previousSibling : null;
    while(node && node.nodeType != 1 )
    {
        node = node.previousSibling;
    }
    
    return node;
}

function contains(a,b)
{
    if(document.defaultView)
    {
        return !!( a.compareDocumentPosition(b) & 16 );
    }else{
        return a != b && a.contains(b);     
    }
} 

/**
children:只有元素节点
childNodes：所有节点
两个都不存在兼容性问题
*/


var lis = document.getElementById('popmenu').getElementsByTagName('li');
for(var i=0;i<lis.length;i++) 
{
    lis[i].onmouseover = function(evt){
        var evt = evt || window.event;
        evt.relatedTarget = evt.relatedTarget || evt.fromElement;

        if(!evt.relatedTarget || !contains(this, evt.relatedTarget))
        {
            //console.log('over')
            next(firstChild(this)).style.display = 'block';
        }
    }
    
    lis[i].onmouseout = function(evt){
        var evt = evt || window.event;
        evt.relatedTarget = evt.relatedTarget || evt.toElement;
        
        if( !evt.relatedTarget || (evt.relatedTarget && !contains(this, evt.relatedTarget)))
        {
            //console.log('out')
            next(firstChild(this)).style.display = 'none';
        }
    }
}
</script>
效果图：