Como faço isso em javascript?

<!DOCTYPE html>
<html>
<head>
    <title>Publicidad</title>
<script type='text/javascript'>
//<![CDATA[
var ftr_arr = new Array();
var ftr_clear = new Array();
function ftrFloat(ftr) {
ftr_arr[ftr_arr.length] = this;
var ftrpointer = eval(ftr_arr.length-1);
this.pagetop = 0;
this.cmode = (document.compatMode && document.compatMode!="BackCompat") ? document.documentElement : document.body;
this.ftrsrc = document.all? document.all[ftr] : document.getElementById(ftr);
this.ftrsrc.height = this.ftrsrc.offsetHeight;
this.ftrheight = this.cmode.clientHeight;
this.ftroffset = ftrGetOffsetY(ftr_arr[ftrpointer]);
var ftrbar = 'ftr_clear['+ftrpointer+'] = setInterval("ftrFloatInit(ftr_arr['+ftrpointer+'])",1);';
ftrbar = ftrbar;
eval(ftrbar);
}

function ftrGetOffsetY(ftr) {
var ftrTotOffset = parseInt(ftr.mtasrc.offsetTop);
var parentOffset = ftr.ftrsrc.offsetParent;
while ( parentOffset != null ) {
ftrTotOffset += parentOffset.offsetTop;
parentOffset = parentOffset.offsetParent;
}
return ftrTotOffset;
}
function ftrFloatInit(ftr) {
ftr.pagetop = ftr.cmode.scrollTop;
ftr.ftrsrc.style.top = ftr.pagetop - ftr.mtaoffset + "px";
}
function closeTopAds() {
document.getElementById("ftr_imagen").style.visibility = "hidden";
}
//]]>


function CheckClose(){
document.all("anuncio").style.visibility="hidden";
}
setTimeout("CheckClose();",20000);

// <![CDATA[

// ]]>
</script>
</head>
<body>
<div id='ftr_imagen'>
<div id="anuncio">
<center><img border='0' class='close' onClick='closeTopAds();return false;' src='http://4.bp.blogspot.com/_qgZA1ny_dAs/S0jtqeCcWUI/AAAAAAAADkA/qLZkUMRn7FU/s200/iconClose.gif'/>
<!--DEBAJO DE ESTO VA LA PUBLICIDAD-->
<script type="text/javascript" src="http://www.adcash.com/script/java.php?option=rotateur&r=440934"></script></center>
<!--ARRIBA DE ESTO VA LA PUBLICIDAD -->
</div>
</div>
</body>
</html>

<div id="texto">
		Esta publicidad se cerrará en <span id="segundos">30</span> segundos.
	</div>
	<div id="adsframe">
		<img class="cerrar" src="cerrar.png">
		<iframe id="ads" src="ads.html" width="300" height="250" frameborder="0"></iframe>
	</div>
	<script type="text/javascript">
var segundosTotal = 30;
var segundos = 30;
var intervalo;
function boton() {
	var cerrar = document.getElementsByClassName('cerrar');
	cerrar[0].style.marginTop = Math.random() * 238 + 0 + 'px';
	cerrar[0].style.marginLeft = Math.random() * 288 + 0 + 'px';
}
function ocultar(id) {
	document.getElementById(id).style.display = 'none';
}
function mostrar(id) {
	document.getElementById(id).style.display = 'block';
}
window.onload = function() {
	var ads = document.getElementById('ads'),
		visible = 1,
		clicks = 0;
	var cerrar = document.getElementsByClassName('cerrar');
	var contar = function() {
		if (segundos > 0) {
			segundos--;
			document.getElementById('segundos').innerHTML = segundos;
			intervalo = setTimeout(contar, 1000);
		} else {
			clearTimeout(intervalo);
			segundos = segundosTotal+1;
			ocultar('adsframe');
			ocultar('texto');
			ads.src = ads.src;
			boton();
			setTimeout(function() {
				mostrar('adsframe');
				mostrar('texto');
				contar();
			}, 4000);
			clicks = 0;
		}
	}
	contar();
	cerrar[0].onclick = function() {
		if (clicks >= 1) {
			clearTimeout(intervalo);
			segundos = segundosTotal+1;
			ocultar('adsframe');
			ocultar('texto');
			ads.src = ads.src;
			boton();
			setTimeout(function() {
				mostrar('adsframe');
				mostrar('texto');
				contar();
			}, 90000);
			clicks = 0;
		} else {
			boton();
			clicks++;
		}
	}
}
boton();
	</script>

<style type="text/css">
#adsframe {
	position: absolute;
	top: 50%;
	left: 50%;
	margin: -134px 0 0 -150px;
	background-color: #FFF;
	z-index: 9998;
	width: 300px;
	height: 250px;
	overflow: hidden;
}
.cerrar {
	position: absolute;
	z-index: 9999;
}
#texto {
	position: absolute;
	text-align: center;
	top: 50%;
	left: 50%;
	width: 300px;
	height: 18px;
	background-color: #FFF;
	margin: -155px 0 0 -150px;
	font-size: 12px;
	padding-top: 3px;
}
	</style>

<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>ADS</title>
	<style type="text/css">
* {
	margin: 0;
	padding: 0;
	overflow: hidden;
}
	</style>
</head>
<body>
	<!-- CODIGO PUBLICIDAD 300X250 -->
	<script type='text/javascript'>
	var adParams = {a: '25172061', size: '300x250',serverdomain: 'adk2trk2.cpmrocket.com'  };
	</script>
	<script type='text/javascript' src='http://adk2cdn.cpmrocket.com/cpmrocket/scripts/smart/smart.js'></script>
	<!-- CODIGO PUBLICIDAD 300X250 -->
</body>
</html>