只从页面上面掉落一次的无边框式窗口，刷新页面时没有效果

- 中国WEB开发者网络 (http://www.webasp.net)
-- 网页特效 (http://www.webasp.net/javascript/)
--- 只从页面上面掉落一次的无边框式窗口，刷新页面时没有效果 (http://www.webasp.net/javascript/1/621.htm)
-- 发布日期： 2005-06-22
<!-- 网页特效代码由[中国WEB开发者网络:http://www.ChinaWebDev.com]提供！ -->
<!-- 要实现此效果需要 1 个步骤： -->

<!-- 第 1 步： -->
<!-- 把下面的代码加到<BODY></BODY>区域中： -->

<script language="JavaScript1.2">
var ie=document.all
var dom=document.getElementById
var ns4=document.layers

var bouncelimit=32 //(must be divisible by 8)
var curtop
var direction="up"
var boxheight=''

function initbox(){
if (!dom&&!ie&&!ns4)
return
crossobj=(dom)?document.getElementById("dropin").style : ie? document.all.dropin : document.dropin
scroll_top=(ie)? document.body.scrollTop : window.pageYOffset
crossobj.top=scroll_top-250
crossobj.visibility=(dom||ie)? "visible" : "show"
dropstart=setInterval("dropin()",50)
}

function dropin(){
scroll_top=(ie)? document.body.scrollTop : window.pageYOffset
if (parseInt(crossobj.top)<100+scroll_top)
crossobj.top=parseInt(crossobj.top)+40
else{
clearInterval(dropstart)
bouncestart=setInterval("bouncein()",50)
}
}

function bouncein(){
crossobj.top=parseInt(crossobj.top)-bouncelimit
if (bouncelimit<0)
bouncelimit+=8
bouncelimit=bouncelimit*-1
if (bouncelimit==0){
clearInterval(bouncestart)
}
}

function dismissbox(){
if (window.bouncestart) clearInterval(bouncestart)
crossobj.visibility="hidden"
}


function get_cookie(Name) {
var search = Name + "="
var returnvalue = ""
if (document.cookie.length > 0) {
offset = document.cookie.indexOf(search)
if (offset != -1) {
offset += search.length
end = document.cookie.indexOf(";", offset)
if (end == -1)
end = document.cookie.length;
returnvalue=unescape(document.cookie.substring(offset, end))
}
}
return returnvalue;
}

function dropornot(){
if (get_cookie("droppedin")==""){
window.onload=initbox
document.cookie="droppedin=yes"
}
}
dropornot()
</script>
<div id="dropin" style="position:absolute;visibility:hidden;left:250;top:100;width:500;height:300;background-color:#F5F5F5">

<div align="right"><a href="javascript:dismissbox()">[关闭窗口] </a></div>
这是只掉一次的窗口
</div>

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