Este no da error, pero sólo acepta mayúsculas. Fijate si te sirve:
Código:
<html>
<head>
<title> Solo numeros y mayúsculas </title>
<script language="JavaScript">
<!--
var nav4 = window.Event ? true : false;
function acceptMay(evt){
var key = nav4 ? evt.which : evt.keyCode;
return (key >= 65 && key <= 90);
}
//-->
</script>
</head>
<body>
<input type=text name="valor2" size=12 maxlength=12 onKeyPress="return acceptMay(event)"><br>
</body>
</html>
<hr noshade size=1><img src="http://www.gograph.com/Images-8712/ClipArt/cat03.gif" height="50" border=0 align="absmiddle"> <font size="2" face="verdana" color="#000000">
bet[/CODE]