Problème javascript?

Bonjour,
J'ai copié sur le site le code java un diaporama tout simple, mais il ne marche pas, voici le code:
<SCRIPT LANGUAGE="JavaScript">

<!-- Begin
browserName = navigator.appName;
browserVer = parseInt(navigator.appVersion);

ns3up = (browserName == "Netscape" && browserVer >= 3);
ie4up = (browserName.indexOf("Microsoft") >= 0 && browserVer >= 4);

function doPic(imgName) {
if (ns3up || ie4up) {
imgOn = ("" + imgName);
document.mainpic.src = imgOn;
}
}
// End -->
</script>

<table width=360 border=0 cellspacing=0 cellpadding=0>
<tr>
<td colspan=4 align=center><img name="mainpic"src="P1000735_360.jpg" alt="img" width="365" height="247"></td>
</tr>
<tr>
<td><a href="javascript:doPic('P1000735_360.jpg');"><img src="P1000735_90.jpg" alt="img" width="90" height="62" border=0></a></td>
<td><a href="javascript:doPic('Lifting-2_360.jpg');"><img src="Lifting-2_360.jpg" alt="img" width="90" height="62" border=0></a></td>
<td><a href="javascript:doPic('DSC00987_360.JPG');"><img src="DSC00987_90.JPG" alt="img" width="90" height="62" border=0></a></td>
<td><a href="javascript:doPic('IMG_0372_360.JPG');"><img src="IMG_0372_90.JPG" alt="img" width="90" height="62" border=0></a></td>
<td> </td>
</tr>
</table>

je tourne en rond, si quelqu'un a la gentillesse de me dépanner merci:))