firefox 下 innerText、innerHTML 的生效问题

firefox下，innerText 无效，innerHTML是生效的

如：

<table id="tableid" border="1">
            <tr>
                <td></td>
                <td></td>
                <td></td>
            </tr>
            <tr>
                <td></td>
                <td></td>
                <td></td>
            </tr>
            <tr>
                <td></td>
                <td></td>
                <td></td>
            </tr>
        </table>

 <script type="text/javascript" >
        var table = document.getElementsByTagName("table")[0];
        var trArr = table.getElementsByTagName("tr").length;
        //var trArr = document.getElementById("tableid").getElementsByTagName("tr").length;//可行
        //alert("行数=" + trArr);
        //动态添加内容
        var button = document.getElementsByTagName("input")[0];
        button.onclick = function () {
            //alert(button.value);
            var tr = table.insertRow();
            for( var i = 0 ; i < 4 ; i++){
                var td = tr.insertCell(i);
                //td.innerText= '新加行'; //无效
                td.innerHTML = "呢";
            }
        }
    </script>