banner es el elemento que yo llame a mi div
div id="banner"
le puse document.getelementbyid voy por mal camino?
<script type="text/javascript">
self.onscroll = function(){
var top = self.pageYOffset || document.body.scrollTop;
var visible = window.innerHeight;
var banner = document.getElementById('banner');
return top > banner.style.height - visible && (banner.style.position = 'fixed');
}
</script>
<div id="banner" style="margin:0px;">
<table width="160" border="0" align="center" cellpadding="0" cellspacing="0">
<tr>
<td width="160" height="600" align="center" bgcolor="#F0F0F0">
<script type="text/javascript">
<!--
google_ad_client = "ca-pub-1895931916113289";
/* vertical derechoo */
google_ad_slot = "9558447790";
google_ad_width = 160;
google_ad_height = 600;
//-->
</script>
<script type="text/javascript"
src="http://pagead2.googlesyndication.com/pagead/show_ads.js">
</script></td>
</tr>
</table>
</div>