Banner chiusura dopo tot secondi

[lucavizzi]

<div style="width: 960px; margin: 0 auto;">
<div style="display: block; text-align: center;">
<div id="banner_left" style="display: block; width: 300px; height: 275px; position: absolute; margin-left: 350px; margin-top: 420px; z-index: 2;">
<p id="chiudi" style="cursor: pointer;"><span style="color: #ff0000;">CHIDI BANNER</span>

<div id="banner"><script BANNER </script></div>
<script type="text/javascript">// <![CDATA[
document.getElementById('chiudi').onclick = closeBanner();
setTimeout(closeBanner(),5000);// chiusura dopo 5 secondi
function closeBanner() { 
    document.getElementById('chiudi').style.display = 'none'; 
    document.getElementById('banner').style.display = 'none'; 
}
// ]]></script>