谁能详细给我讲讲marquee无间隙的连续滚动效果的做法！

-----------------------上下滚动主要部分-------------------------
<!-- 图片宽度width:90 图片高度height:150 背景颜色background:#214984 这些根据你实际的需要修改-->
<div id=demo style=overflow:hidden;height:150;width:90;background:#214984;color:#ffffff>
<div id=demo1>
<!-- 加入要滚动的内容 -->
<!--#include file="GX/PHOTOIMG.htm"--></div>
<div id=demo2></div>
</div>
-----------------------向上滚动-------------------------------
<script>
var speed=30
demo2.innerHTML=demo1.innerHTML
function Marquee(){
if(demo2.offsetTop-demo.scrollTop<=0)
demo.scrollTop-=demo1.offsetHeight
else{
demo.scrollTop++
}
}
var MyMar=setInterval(Marquee,speed)
demo.onmouseover=function() {clearInterval(MyMar)}
demo.onmouseout=function() {MyMar=setInterval(Marquee,speed)}
</script>
-----------------------向下滚动-------------------------------
<script>
var speed=30
demo2.innerHTML=demo1.innerHTML
demo.scrollTop=demo.scrollHeight
function Marquee(){
if(demo1.offsetTop-demo.scrollTop>=0)
demo.scrollTop+=demo2.offsetHeight
else{
demo.scrollTop--
}
}
var MyMar=setInterval(Marquee,speed)
demo.onmouseover=function() {clearInterval(MyMar)}
demo.onmouseout=function() {MyMar=setInterval(Marquee,speed)}
</script>
-----------------------左右滚动主要部分--------------------------
<!-- 图片宽度width:90 图片高度height:150 背景颜色background:#214984 这些根据你实际的需要修改-->
<div id=demo style=overflow:hidden;height:100;width:600;background:#214984;color:#ffffff>
<table align=left cellpadding=0 cellspace=0 border=0>
<tr>
<td id=demo1 valign=top<!--#include file="GX/PHOTOIMG.htm"-->
</td>
<td id=demo2 valign=top></td>
</tr>
</table>
</div>
-----------------------向左滚动-------------------------------
<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>
-----------------------向右滚动-------------------------------
<script>
var speed=30
demo2.innerHTML=demo1.innerHTML
demo.scrollLeft=demo.scrollWidth
function Marquee(){
if(demo.scrollLeft<=0)
demo.scrollLeft+=demo2.offsetWidth
else{
demo.scrollLeft--
}
}
var MyMar=setInterval(Marquee,speed)
demo.onmouseover=function() {clearInterval(MyMar)}
demo.onmouseout=function() {MyMar=setInterval(Marquee,speed)}
</script>