xt" name="valistr" id="valistr" onblur="checkNull('valistr', '验证码不能为空')"/>
                <img width="" height="" alt="验证码" onclick="refreshValistr(this)"/>
                <span style="color: red" id="valistr_msg"></span>
            </td>
        </tr>
        <tr>
            <td class="sub_td" colspan="2" >
                <input type="submit" value="注册用户"/>
            </td>
        </tr>
    </table>
</form>
</body>
</html>