用js控制div的显示和隐藏。

div.style.display = "none" 和 div.style.display = "block"。

页面代码：


<!DOCTYPEhtml PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<htmlxmlns="http://www.w3.org/1999/xhtml">
<head>
    <title></title>
 
    <script type="text/javascript">
        var count = 0; //做计数器
        var limit = new Array(); //用于记录当前显示的哪几个菜单
        var countlimit = 1; //同时打开菜单数目，可自定义
 
        function
            obj = eval（"sub"
            if (obj.style.display == "none") {
                obj.style.display = "block"; //显示子菜单
                if (count < countlimit) {//限制2个
                    limit[count] = el; //录入数组
                    count++;
                }
                else
                    eval（"sub" + limit[0]).style.display = "none";
                    for (i = 0; i < limit.length - 1; i++) { limit[i] = limit[i + 1]; } //数组去掉头一位，后面的往前挪一位
                    limit[limit.length - 1] = el;
                }
            }
            else
                obj.style.display = "none";
                var
                for (i = 0; i < limit.length; i++) { if (limit[i] == el) j = i; } //获取当前点击的菜单在limit数组中的位置
                for (i = j; i < limit.length - 1; i++) { limit[i] = limit[i + 1]; } //j以后的数组全部往前挪一位
                limit[limit.length - 1] = null; //删除数组最后一位
                count--;
            }
        }
    </script>
 
</head>
<body>
    <div id="main1" onclick="expandIt(1)">
        <table width="170" height="24" border="0" cellpadding="0" cellspacing="0">
            <tr style="cursor: hand;">
                <td width="26">
                </td>
                <td class="SystemLeft">
                    企业信息
                </td>
            </tr>
        </table>
    </div>
    <div id="sub1" style="display: none">
        <table width="160" border="0" cellspacing="0" cellpadding="0">
            <tr>
                <td width="36" height="22">
                </td>
                <td class="SystemLeft">
                    <a href="AboutList.asp" target="mainFrame" onclick='changeAdminFlag("企业信息列表")'>企业信息列表</a>
                </td>
            </tr>
            <tr>
                <td width="36" height="22">
                </td>
                <td class="SystemLeft">
                    <a href="AboutEdit.asp?Result=Add" target="mainFrame" onclick='changeAdminFlag("添加企业信息")'>
                        添加企业信息</a>
                </td>
            </tr>
        </table>
    </div>
    <div id="main2" onclick="expandIt(2)">
        <table width="170" height="24" border="0" cellpadding="0" cellspacing="0">
            <tr style="cursor: hand;">
                <td width="26">
                </td>
                <td class="SystemLeft">
                    新闻资讯
                </td>
            </tr>
        </table>
    </div>
    <div id="sub2" style="display: none">
        <table width="160" border="0" cellspacing="0" cellpadding="0">
            <tr>
                <td width="36" height="22">
                </td>
                <td class="SystemLeft">
                    <a href="NewsSort.asp?Action=Add&ParentID=0" target="mainFrame" onclick='changeAdminFlag("新闻类别")'>
                        新闻类别</a>
                </td>
            </tr>
            <tr>
                <td width="36" height="22">
                </td>
                <td class="SystemLeft">
                    <a href="NewsList.asp" target="mainFrame" onclick='changeAdminFlag("新闻列表")'>新闻列表</a>
                </td>
            </tr>
            <tr>
                <td width="36" height="22">
                </td>
                <td class="SystemLeft">
                    <a href="NewsEdit.asp?Result=Add" target="mainFrame" onclick='changeAdminFlag("添加新闻")'>
                        添加新闻</a>
                </td>
            </tr>
        </table>
    </div>
    <div id="main3" onclick="expandIt(3)">
        <table width="170" height="24" border="0" cellpadding="0" cellspacing="0">
            <tr style="cursor: hand;">
                <td width="26">
                </td>
                <td class="SystemLeft">
                    产品展示
                </td>
            </tr>
        </table>
    </div>
    <div id="sub3" style="display: none">
        <table width="160" border="0" cellspacing="0" cellpadding="0">
            <tr>
                <td width="36" height="22">
                </td>
                <td class="SystemLeft">
                    <a href="ProductSort.asp?Action=Add&ParentID=0" target="mainFrame" onclick='changeAdminFlag("产品类别")'>
                        产品类别</a>
                </td>
            </tr>
            <tr>
                <td width="36" height="22">
                </td>
                <td class="SystemLeft">
                    <a href="ProductList.asp" target="mainFrame" onclick='changeAdminFlag("产品列表")'>产品列表</a>
                </td>
            </tr>
            <tr>
                <td width="36" height="22">
                </td>
                <td class="SystemLeft">
                    <a href="ProductEdit.asp?Result=Add" target="mainFrame" onclick='changeAdminFlag("添加产品")'>
                        添加产品</a>
                </td>
            </tr>
        </table>
    </div>
</body>
</html>