radio checked不起作用的原因

 <table  id="approveTable">
                    <tr>
                       <td>
                        <input  type="radio"   name="action"  value="1"  checked="checked"   onclick='$("#selectRow").css("visibility","visible");'/>成功
                        </td>
                        <td>
                        <input  type="radio"   name="action"   value="0"  onclick='$("#selectRow").css("visibility","hidden");'/>失败
                        </td>
                    </tr>
</table>

这种方式checked是起作用,但如果不把控件包在td中就不起作用了,如下：

 <table  id="approveTable">
                    <tr>

                        <input  type="radio"   name="action"  value="1"  checked="checked"   onclick='$("#selectRow").css("visibility","visible");'/>成功

                        <input  type="radio"   name="action"   value="0"  onclick='$("#selectRow").css("visibility","hidden");'/>失败

                    </tr>
</table>