[HTML] pobierz, plaintext 
<div id="dropin" style="position:absolute; visibility:hidden; left:400px; top:400px; width:auto; height:auto; background-color:#F5F5F5">
[HTML] pobierz, plaintext 

var ie=document.all
var dom=document.getElementById
var ns4=document.layers
var calunits=document.layers? "" : "px"
var bouncelimit=32
var direction="up"

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

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

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

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

function truebody(){
return (document.compatMode && document.compatMode!="BackCompat")? document.documentElement : document.body
}
window.onload=initbox

.belka {
      position: fixed;
      top:0px;
      width:100%;
      height:100%;
      display:none;
      text-align:center;
      background-color:transparent;
      margin:0px;
      left:0px;
      z-index: 1;
}
* html .belka {
      position: absolute;
      top: expression(parseInt((document.body.scrollTop||documentElement.scrollTop))+'px');
}

<div class="belka">...</div>

crossobj.top = '100px';

crossobj.style.top = '100px';