一个脚本问题

<script type="text/javascript">  function AddZhiwei() {            var tab = document.getElementById("zwtab");
            for (var i = 0; i < 1; i++) {
                var newTr = tab.insertRow(tab.rows.length);
                for (var j = 0; j < tab.rows[0].cells.length; j++) {
                    newTd = newTr.insertCell(j);
                }
                newTr.cells[0].innerHTML = "<input  type='text' name='txtTime'onfocus='WdatePicker({skin:'blue',dateFmt:'yyyy-MM-dd'});' Width='100px'/>";
                newTr.cells[1].innerHTML = "<input  type='text' name='z_text' />";
                newTr.cells[2].innerHTML = "<img   src='../../images2/icon_add.gif' alt='增加职位信息' onclick='AddZhiwei();' />&nbsp;&nbsp;<img src='../../images2/icon_delete.gif' onclick='DeleteRow(this)' alt='删除职位信息' />"
            }
        } </script>   
<table id="zwtab" class="mygridview">
                        <tr class="styleTd1">
                            <th align="center">
                                时间
                            </th>
                            <th align="center">
                                职位
                            </th>
                            <th align="center">
                                操作
                            </th>
                        </tr>
                        <tr>
                            <td>
                                <input id="txtTime" type="text" name="txtTime"  onfocus="WdatePicker({skin:'blue',dateFmt:'yyyy-MM-dd'});" Width="100px" />
                            </td>
                            <td>
                                <input id="txtzw" type="text" name="z_text" />
                            </td>
                            <td>
                                <img id="imgAdd" runat="server" src="../../images2/icon_add.gif" alt="增加职位信息" onclick="AddZhiwei();" />&nbsp;&nbsp;
                                <img src="../../images2/icon_delete.gif" onclick="DeleteRow(this)" alt="删除职位信息" />
                                <input id="hidZW" type="hidden" runat="server" />
                            </td>
                        </tr>
                    </table>
点击增加的时候，报个脚本错误是为什么啊