有几个地方可能有问题：
部分浏览器不支持form1.这种方法访问控件，使用document.方法。
if(elements[i].type=='checkbox') {
if(elements[i].checked==false){
elements[i].checked=true}}
这样写会比较好点：
if (elements[i].type == 'checkbox') elements[i].checked = !elements[i].checked
<!DOCTYtrE html trUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "htttr://<html xmlns="htttr://
<head>
<meta htttr-equiv="Content-Tytre" content="text/html charset=utf-8" />
<title>Example 1</title>
<script type="text/javascript">
function validate(form){
var returnValue=true
var name=form.fname.value
if(name==""){
returnValue=false
alert("You must enter a name")
document.example.txtname.focus()
}
var email=form.femail.value
var rxemail= /^([a-zA-Z0-9]+[_|\_|\.]?)*[a-zA-Z0-9]+@([a-zA-Z0-9]+[_|\_|\.]?)*[a-zA-Z0-9]+\.[a-zA-Z]{2,3}$/
if(!rxemail.test(email)){
returnValue=false
alert("You must enter a valid email address")
document.example.femail.focus()
}
var radiochosen=false
var radiobuttons=form.fanswer
for(var i=0i<radiobuttons.lengthi++){
if(radiobuttons[i].checked){
radiochosen=true
}
}
if(radiochosen==""){
returnValue=false
alert("You did not answer the question")
document.example.fanswer.focus()
}
var tiebreak=form.textbreak.value
if(tiebreak==""){
returnValue=false
alert("Youu must enter an answer for the tie breaker")
document.example.textbreak.focus()
}
var tiebreaklength=textbreak.split(/\s+/g)
wordcount=tiebreaklength.length
if(wordcount>20){
returnValue=false
alert("Your tie breaker answer must be no more than 20 words. You entered "+wordcount+" words.")
document.example.textbreak.focus()
}
return returnValue
}
</script>
</head>
<body>
<form name="example" method="post" action="competiotion.aspx" onSubmit="return validate(this)">
<h1>An Example Competition Form</h1>
<h1>(Sorry,there are no real prizes!)</h1>
<p>To enter the drawing to win a case of Jenny's Jam,first answer this question"What color are strawberries?"Then provide an answer for the tie-breaker question "I would like to win a case of Jenny's Jam because..." in no more than 20 words.</p>
<table align="center">
<tr>
<td class="fname">Name:</td>
<td><input type="text" id="fname" size="30" /></td>
</tr>
<tr>
<td class="femail">Email:</td>
<td><input type="text" id="femail"size="30" />
</td>
</tr>
<tr>
<td class="fanswer">Answer:</td>
<td><input type="radio" value="red" name="fanswer" />Red<br />
<input type="radio" value="gray" name="fanswer" />Gray<br />
<input type="radio" value="blue" name="fanswer" />Blue
</td>
</tr>
<tr>
<td class="fbreak">Tie breaker<br />(no more than 20 words):</td>
<td><textarea rows="5" cols="30" name="textbreak" style="overflow-y:hidden"></textarea>
</td>
</tr>
<tr>
<td></td>
<td><input type="submit" value="Enter now" /></td>
</tr>
</table>
</form>
</body>
</html>
给你修改了一下，因为你的表单id和name没有跟js的对应上
比如 var name=form.fname.value这个是获取用户名
那么用户名的input就应该是<input type="text" id="fname" size="30" />（注意id）
