js左滚动代码问题

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>123</title>
</head>

<body>
<table width="740" border="0" cellspacing="0" cellpadding="0">
       <tr>
        <td width="29"><img src="/Skin/images/yueqi_23.jpg" width="29" height="137" onclick="MarqueeML()" /></td>
        <td align="center" class="yeqi_main_06">
<div id=demo style="overflow:hidden;width:660px;" align=center>
    <table border=0 align=center cellpadding=0 cellspacing=0 cellspace=0 width="2500">
        <tr><td id=marquePic1>
          <table border="0" cellpadding="0" cellspacing="0">
              <tr>
                <td><img src="/Skin/images/yueqi_25.jpg" width="113" height="99" /> <img src="/Skin/images/yueqi_25.jpg" width="113" height="99" /> <img src="/Skin/images/yueqi_25.jpg" width="113" height="99" /> <img src="/Skin/images/yueqi_25.jpg" width="113" height="99" /> <img src="/Skin/images/yueqi_25.jpg" width="113" height="99" /> <img src="/Skin/images/yueqi_25.jpg" width="113" height="99" /> <img src="/Skin/images/yueqi_25.jpg" width="113" height="99" /> <img src="/Skin/images/yueqi_25.jpg" width="113" height="99" /> <img src="/Skin/images/yueqi_25.jpg" width="113" height="99" /> <img src="/Skin/images/yueqi_25.jpg" width="113" height="99" /></td>
              </tr>
            </table>

</td><td id=marquePic2 valign=top></td></tr>
    </table></div>
<script type="text/javascript">
var speed=50 
marquePic2.innerHTML=marquePic1.innerHTML 
function MarqueeL(){ 
if(demo.scrollLeft>=marquePic1.scrollWidth){ 
demo.scrollLeft=0 
}else{ 
demo.scrollLeft++ 
} 
}

function MarqueeR(){ 
if(demo.scrollLeft>=marquePic1.scrollWidth){ 
demo.scrollLeft=0 
}else{ 
demo.scrollLeft-- 
} 
}

var MyMar=setInterval(MarqueeL,speed)
demo.onmouseover=function() {clearInterval(MyMar)} 
demo.onmouseout=function() {MyMar=setInterval(MarqueeL,speed)} 

function MarqueeML(){ 
var MyMar=setInterval(MarqueeL,speed)
demo.onmouseover=function() {clearInterval(MyMar)} 
demo.onmouseout=function() {MyMar=setInterval(MarqueeL,speed)} 
}

function MarqueeMR(){ 
var MyMar=setInterval(MarqueeR,speed)
demo.onmouseover=function() {clearInterval(MyMar)} 
demo.onmouseout=function() {MyMar=setInterval(MarqueeR,speed)} 
}
</script>
          </td>
        <td width="29"><img src="/Skin/images/yueqi_24.jpg" width="29" height="137" onclick="MarqueeMR()" /></td>
       </tr>
    </table>
</body>
</html>

 

 

要做一个带左右箭头控制的图片横向滚动效果，点击左箭头图片向左滚动，点击右箭头图片向右滚动，点击左箭头没有问题，点击右箭头有问题，代码要怎么改，请教大家，我对js代码不太熟

我看了你代码，你这是滚动加速啊，点的次数越多滚动速度越快，相反就是减速，减到0时就往反方向滚动。
左右都可以滚动。