Banner Alignment Problem

[jfiliss]

I'm trying to keep my banners centered, but often and unexpectedly they align to the right. Any ideas what I'm doing wrong here, or what a better way to do this would be? I'm using a div tag surrounding my invocation code (below). Thanks!

<div align="center"><script language='JavaScript' type='text/javascript'> 
<!-- 
if (!document.phpAds_used) document.phpAds_used = ','; 
document.write ("<" + "script language='JavaScript' type='text/javascript' src='"); 
document.write ("http://www.com/ads/adjs.php?n=ab4caa88"); 
document.write ("&amp;what=zone:7&amp;target=_blank"); 
document.write ("&amp;exclude=" + document.phpAds_used); 
if (document.referer) 
document.write ("&amp;referer=" + escape(document.referer)); 
document.write ("'><" + "/script>"); 
//--> 
</script><noscript> 
<a href='http://www.com/ads/adclick.php?n=ab4caa88' 
target='_blank'><img src='http://www.com/ads/adview.php?
what=zone:10&amp;n=ab4caa88' border='0' alt=''></a></noscript></div>