<script type="text/javascript">
function beforeSubmit(form){
if(form.username.value==''){
alert('使用者名稱不能為空！');
form.username.focus();
return false;
}
if(form.password.value==''){
alert('密碼不能為空！');
form.password.focus();
return false;
}
if(form.password.value.length<6){
alert('密碼至少為6位，請重新輸入！');
form.password.focus();
return false;
}
if(form.password.value!=form.password2.value) {
alert('你兩次輸入的密碼不一致，請重新輸入！');
form.password2.focus();
return false;
}
return true;
}
</script>

<fieldset>
   <legend>使用者註冊</legend>
    <form method="post" name="form" action="user.do?method=register" onSubmit="return beforeSubmit(this);">
     <table border="1" width="100%" cellspacing="0" cellpadding="0">
      <tr><td><label>使用者名稱：<input type="text" name="username" value=""></label></td></tr>
      <tr><td><label>密   碼：<input type="password" name="password" value=""></label></td></tr>
      <tr><td><label>重複密碼：<input type="password" name="password2" value=""></label></td></tr>
      <tr><td><input value="註冊" type="submit"> <input type="reset" value="重置"></td></tr>      
     </table>
    </form>
</fieldset>