网页不间断跑马灯效果实现与代码解析

<div align="center" id="dsmo" style="overflow:hidden; height:200px; width:99%; border-width:0; border-style:dotted dotted dotted dotted;">
    <div id="dsmo1">
        <!-- 定义内容-->
<iframe frameborder="0" id="main" name="main" scrolling="no" allowTransparency="true" src="news/company_view.asp?id=<% dim lrsView,lsqlView,lIDView
  set lrsView=server.CreateObject("adodb.recordset")
  lsqlView="select * from NewsData where D_CataID like '%A00060008%'"
  lrsView.open lsqlView,oConn,0,1
  if not lrsView.eof then
  lIDView = lrsView("D_ID")
  Response.Write lrsView("D_ID") 
  Else
  Response.Write ""
end if
  
  %>" style="background-color:transparent; HEIGHT: 220px; VISIBILITY: visible; WIDTH: 100%; Z-INDEX: 0"></iframe>           </div>
    <div id="dsmo2"></div>
</div>
<script language="javascript" type="text/javascript">
<!--
var dsmo = document.getElementById("dsmo");
var dsmo1 = document.getElementById("dsmo1");
var dsmo2 = document.getElementById("dsmo2");
var speeds=50;    //滚动速度值，值越大速度越慢
dsmo2.innerHTML = dsmo1.innerHTML    //克隆dsmo2为dsmo1
function Marquee(){
    if(dsmo2.offsetTop-dsmo.scrollTop<=0)    //当滚动至dsmo1与dsmo2交界时
        dsmo.scrollTop-=dsmo1.offsetHeight    //dsmo跳到最顶端
    else{
        dsmo.scrollTop++
    }