<script language="javascript">
<!--
function Juge()
{
if(isNaN(sz.shuzi.value)){
alert("请您输入正确而且符合条件的数字");
sz.shuzi.focus();
sz.shuzi.value=""
return (false);
}
else
{
alert("输入正确！");
}
}
//-->
</script>
<body>
<form name=sz>
<input type=text name=shuzi size=20><input type=button onclick="Juge()" value=数字校验>
</form>
</body>