大虾们帮忙看看，老弟是新手，写了个简单的页面老是出错
帮我看下下面这段程序有什么错误．共有１２个按钮，第一个和最后一个实现翻页功能，使中间按纽的值分别减一和加一．按纽的值只能是１到５０<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=windows-1250">
<meta name="generator" content="PSPad editor, www.
<title></title>
<script language="JavaScript" type="text/javascript">
function change0()
{
var objs = document.all["a"];
var b=objs.length;
for(i=0;i<b;i++)
objs[i].value=parseInt(objs[i].value)-10;
if (parseInt(objs[0].value)=1) document.form[0].buttonp.style.display="none";
if (parseInt(objs[0].value)=!41) document.form[0].buttonn.style.display="block";
//for(i=0;i<b;i++)
//objs[i].value=parseInt(objs[i].value)-10;
}
function change1()
{var objs = document.all["a"];
var b=objs.length;
for(i=0;i<b;i++)
objs[i].value=parseInt(objs[i].value)+10;
if (parseInt(objs[0].value)!=1) document.form.buttonp.style.display="block";
if (parseInt(objs[0].value)=41) document.form.buttonn.style.display="none";
// for(i=0;i<b;i++)
// objs[i].value=parseInt(objs[i].value)+10;
}
</script>
</head>
<body>
<form name=form1>
<input name="buttonp" type="button" value="previous" style="display:none" onclick="change0()">
<input name="button1" id="a" type="button" value="1">
<input name="button1" id="a" type="button" value="2">
<input name="button1" id="a" type="button" value="3">
<input name="button1" id="a" type="button" value="4">
<input name="button1" id="a" type="button" value="5">
<input name="button1" id="a" type="button" value="6">
<input name="button1" id="a" type="button" value="7">
<input name="button1" id="a" type="button" value="8">
<input name="button1" id="a" type="button" value="9">
<input name="button1" id="a" type="button" value="10">
<input name="buttonn" type="button" value="next" onclick="change1()">
</form>
</body>
</html>
