全境封锁快速升级攻略:网页高手来看看

<tr>
<td height="150" bgcolor="#FFFFF4" width="540">
<table border="0" width="536" id="table19" height="151" cellspacing="0" cellpadding="0">
<tr>
<td>
<style type="text/css">
<!--
body {
background-color: #FCF5EB;
topmargin:0;
leftmargin:0;
}
-->
</style>
<DIV id=demo style="OVERFLOW: hidden; WIDTH: 539px; height:153px">

<TABLE border=0 align=center cellPadding=0 cellspacing="0" cellspace="0" width="524" height="150">
<TBODY>
<TR>
<TD id=demo1 width="469">
<table width="178" border="0" cellpadding="0" cellspacing="0" bgcolor="#FCF5EB" height="144">
<tr align="center">

<td width="90"><img src="image/产品预览1.jpg" width="178" height="150" border="0" class=box></td>

<td width="90"><img src="image/产品预览2.jpg" width="178" height="150" border="0" class=box></td>

<td width="90"><img src="image/产品预览3.jpg" width="178" height="150" border="0" class=box></td>

</tr>
</table>
</TD>
<TD vAlign=bottom bgcolor="#FCF5EB" id=demo2 width="0"></TD>
</TR>
</TBODY>
</TABLE>
</DIV>
<DIV id=demo3 style="OVERFLOW: hidden; WIDTH: 0px; height:1px"></DIV>
<SCRIPT>
var speed=40
demo2.innerHTML=demo1.innerHTML
function Marquee(){
if(demo2.offsetWidth-demo.scrollLeft<=0)
demo.scrollLeft-=demo1.offsetWidth
else{
demo.scrollLeft++
}
}
var MyMar=setInterval(Marquee,speed)
demo.onmouseover=function() {clearInterval(MyMar)}
demo.onmouseout=function() {MyMar=setInterval(Marquee,speed)}
</SCRIPT></td>
</tr>
</table>

</td>
</tr>
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这段代码有什么错误吗??为什么它每次只滚动一圈就停了呢?!我是新手,不要笑我呀