修改滚动的一个方向，谁会？

Question

左右滚动demo的宽度要比demo1.offsetWidth要小,同理上下滚动demo的高度要比demo1.offsetHeight要小
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<style>
img {
display:block
}
</style>
<div id=demo style=overflow:hidden;height:131;width:88;background:#214984;color:#ffffff>
<table cellpadding=0 cellspacing=0 border=0 width="100%"><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"></td>
<tr> <td id=demo2 valign=top></td></tr></table></div>
<script>
var speed=30
demo2.innerHTML=demo1.innerHTML
function Marquee(){
if(demo2.offsetHeight-demo.scrollTop<=0)
demo.scrollTop-=demo2.offsetHeight
else{
demo.scrollTop++
}
}
function Marquee2(){
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>
<input type="button" value="click" onclick="alert(demo2.offsetHeight)"><input type="button" value="click" onclick="alert(demo.scrollTop)">