这个问题是怎么了？
界面有个checkbox，它的代码如下：
<tr>  
                                    <td   width= "80 "   align= "right "> 主题： </td>
                                    <td> <input   name= "Subject "   type= "text "   id= "Subject "   size= "30 "   maxlength= "255 "> &nbsp;&nbsp; <input   type= "checkbox "   id= "chk "   name= "chk "   value= "false "   onClick= "show(); "> 是否设定广告标题 </td>
                                </tr>


                                <tr>
                                    <td   colspan= "2 ">
    <table   width= "100% "     border= "0 "   cellspacing= "0 "   cellpadding= "0 "   class= "NormalText "   style= "display:none "   id= "tb ">
    <tr>
        <td   width= "17% "   height= "26 "   align= "right "> 广告语标题： </td>
        <td   width= "83% "> <input   type= "text "   size= "30 "   maxlength= "20 "   id= "EJSubject "   name= "EJSubject "> &nbsp;&nbsp; <font   color= "red "> （备注：E京标题字数不能超过20个字符） </font> </td>
    </tr>
</table>     </td>
                                </tr>

show()的函数为：
<script   language=javascript>
function   show(){
{
if(document.getElementById( "chk ").checked=true)
{
document.all[ "tb "].style.display= "block ";
}
else
{
document.all[ "tb "].style.display= "none ";
}
}
</script>

为啥出现错误呢？谢谢！

------解决方案--------------------
我测试了很正常，就把你的那段前后加上 <table> 封起来，如下：

<table>
<tr>
<td width= "80 " align= "right "> 主题： </td>
<td> <input name= "Subject " type= "text " id= "Subject " size= "30 " maxlength= "255 "> &nbsp;&nbsp; <input type= "checkbox " id= "chk " name= "chk " value= "false " onClick= "show(); "> 是否设定广告标题 </td>
</tr>


<tr>
<td colspan= "2 ">
<table width= "100% " border= "0 " cellspacing= "0 " cellpadding= "0 " class= "NormalText " style= "display:none " id= "tb ">
<tr>
<td width= "17% " height= "26 " align= "right "> 广告语标题： </td>
<td width=