为什么我这段连续横向滚动的js程序只滚动一次就不动了？

Question

页面打开时，横向滚动正常，但第一次滚动完后，就停止了，是怎么回事？<TABLE id="Table14" cellSpacing="1" cellPadding="1" width="100%" align="center" border="0">
<TR>
<TD vAlign="middle"><IMG src="pic/hot_produce.gif"></TD>
<TD vAlign="middle" width="100%">
<div id="demo" style="OVERFLOW: hidden; WIDTH: 530px; HEIGHT: 160px">
<div id="demo1" runat="server"></div>
<div id="demo2"></div>
</div>
<script>
var speed=30
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>
<TD vAlign="middle"><IMG src="pic/hot_produce.gif"></TD>
</TR>
</TABLE>

Answer 1

<div id=demo style=overflow:hidden;height:33;width:500;background:#214984;color:#ffffff><table align=left cellpadding=0 cellspace=0 border=0><tr><td id=demo1 valign=top><img src="http://netbei.com/logo.gif"><img src="http://netbei.com/logo.gif"><img src="http://netbei.com/logo.gif"><img src="http://netbei.com/logo.gif"><img src="http://netbei.com/logo.gif"><img src="http://netbei.com/logo.gif"><img src="http://netbei.com/logo.gif"><img src="http://netbei.com/logo.gif"><img src="http://netbei.com/logo.gif"></td><td id=demo2 valign=top></td></tr></table></div>
<script>
var speed=30
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>