jquery问题用的时候报错Cannot call method 'ready' of null

Question

报错：15Uncaught TypeError: Cannot call method 'ready' of null
请问是什么原因？谢谢回答
部分代码如下：<script type="text/javascript" src="scripts/jquery-1.6.2.min.js"></script><script type="text/javascript" src="scripts/controls.js"></script>
<SCRIPT type="text/Javascript" src="scripts/select.js"></SCRIPT>
<script type="text/JavaScript">
$(document).ready(function(){
/* $("#Kpbs56").checkRange({
onFocus:"年龄为数字",
onEmpty:"不能为空",
onSucces:"验证成功",
onBlur:"验证失败,请认真输入",
dataType:"number",
min:"0",
max:"56",
tipId:"txtAgeTip",
}); */
}); 
</script>
<fieldset>
            <legend align="center">Video Crop Setting</legend>
            <table width="100%">
                <tr>
                    <td width="4%"></td>
                    <td width="48%">
                        <div class="under_control">
                            Top/Bottom<span>[0,56]</span>:<input type="text" id="Kpbs56" name="Kpbs" value="0" size="3"/>
                        </div>
                        <div class="control">
                                
                        </div>
                    </td>
              
                    <td width="48%">
                        <div class="under_control">
                         Left/Right<span>[0,320]</span>:<input type="text" name="Kpbs" value="0" size="3" />
                        </div>
                        <div class="control">
                          
                        </div>
                    </td>
                </tr>
            </table>
            </fieldset>

Answer 1

<script type="text/JavaScript">
$(document).ready(function(){
    /* $("#Kpbs56").checkRange({
        onFocus:"年龄为数字",
        onEmpty:"不能为空",
        onSucces:"验证成功",
        onBlur:"验证失败,请认真输入",
        dataType:"number",
        min:"0",
        max:"56",
        tipId:"txtAgeTip",
        }); */
}); 
</script>
你不写实现，不调用这个方法放在页面上干嘛？

Answer 2

其实就是想做个文本输入框限制的功能，最大输入0-n 只能是数字
<input type="text" name="Kpbs" value="0" size="3" />

Answer 3

问题找到了是和这个冲突了！<SCRIPT type="text/Javascript" src="scripts/select.js"></SCRIPT>