颜色滚动效果

<!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=utf-8" />
<title>无标题文档</title>
<script language="javascript" type="text/javascript">
var timeId = setInterval("sroll()",200);
function sroll(){

var tables = document.getElementById("tables");
var colors = new Array();
var tds = tables.getElementsByTagName("td");
for(var i=0;i<tds.length;i++){
   var dd = tds[i];
   colors[i]=dd.style.backgroundColor;
  }
for(var i=0;i<tds.length;i++){
  var td = tds[i];
  var tr;
  if(i-1<0){
   tr=colors[colors.length-1];
  }
  else{
   tr=colors[i-1];
  }
  td.style.background = tr;
}
}
function stopSroll(){
clearInterval(timeId);
}
</script>
</head>

</table>
<p>
<input type="button" value="stop" onclick="stopSroll()" style="300px; height:100px" />
</p>
</body>
</html>