IE6、IE7、IE8 都兼容 下拉菜单

<style type="text/css">      
 .menu_iframe
            {
                position: absolute;
                visibility: inherit;
                top: 0px;
                left: 0px;
                width: 145px;
                z-index:-1;
                filter: Alpha(Opacity=0);
            }
            #nav, #nav ul
            {
              border-left: 1px solid Linen;
              border-top: 1px solid Linen;
              border-bottom: 1px solid Linen;
              float: left; /* 菜单总体水平位置 */
              list-style: none;
              line-height: 22px; /* 一级菜单高 */
             background: Linen; /* 所有菜单移出色 */
             font-weight: bold;
             padding: 0px;
            margin: 0px;
            border-right: 0px;
            height: 18px;
        }
            #nav a
            {
                width: 100px;
                display: block;
                color: #ff8006;
                text-decoration: none;
                text-align: center;
                border-right: 1px solid Linen;
            }
            #nav a:hover
            {
                color: #ff8006;
            }
            /* 所有 a:hover 字体样式 */
            #nav li
            {
                float: left;
             
            }
            #nav li ul
            {
                /* 二级弹出位 */
                position: absolute;
                margin: 0px 0px 0px -1px;
                padding: 0;
                left: -9999em;
                width: 120px;
                font-weight: normal;
                 
            }
            #nav li li
            {
                width: 100px;
               
            }
            /* 二级菜单宽 */
            #nav li ul a
            {
                width: 120px; /* 二级菜单宽 */
                padding: 0px 12px;
                line-height: 24px; /* 二级菜单高 */
                border-top: 0px;
                text-align: left;
                border-bottom: 1px solid #FFFFFF;  
               
            }
            #nav li:hover ul ul, #nav li.sfhover ul ul
            {
                left: -9999em;
                
            }
            #nav li:hover ul, #nav li li:hover ul, #nav li.sfhover ul, #nav li li.sfhover ul
            {
                left: auto;
            }
            /* 所有弹出菜单自动左边距 */
            #nav li:hover, #nav li.sfhover
            {
                background: Linen;
            }
            /* 所有悬浮样式 */
     
    </style> <script type="text/javascript">
        sfHover = function() {
            var sfEls = document.getElementById("nav").getElementsByTagName("LI");
            for (var i = 0; i < sfEls.length; i++) {
                sfEls[i].onmouseover = function() {
                    this.className += " sfhover";
                };
                sfEls[i].onmouseout = function() {
                    this.className = this.className.replace(new RegExp(" sfhover\\b"), "");
                };
            }
        };
        window.onload = sfHover;
       </script>
 <div style=" width:100%; z-index:99;">
             <ul id="nav">
                 <li><a href="#">工单跟進</a></li>
                 <li><a href="#">报表查询</a>
                    <ul>
                         <li><a href="Report/ACDReport.aspx" target="_bank">ACD Report</a></li>
                         <li><a href="Report/TDCBrandNewReport.aspx" target="_bank">TDC Brand New Report</a></li>
                         <li><a href="Report/ACDReport.aspx" target="_bank">ACD Report</a></li>
                         <li><a href="Report/ACDReport.aspx" target="_bank">ACD Report</a></li>
                         <iframe class="menu_iframe"></iframe>
                    </ul>
                     
                </li>
            </ul>
        </div>
   <div style="width: 98%; height: 22px; margin: auto; margin-top:10px;" >
            <span style="float: left; width: 400px;" >狀態：<asp:DropDownList ID="DropDownListStatus"
                runat="server" Width="250px" >
            </asp:DropDownList>
</div>