messages: {

     required: "This field is required.",

     remote: "Please fix this field.",

     email: "Please enter a valid email address.",

     url: "Please enter a valid URL.",

     date: "Please enter a valid date.",

     dateISO: "Please enter a valid date ( ISO ).",

     number: "Please enter a valid number.",

     digits: "Please enter only digits.",

     creditcard: "Please enter a valid credit card number.",

     equalTo: "Please enter the same value again.",

     maxlength: $.validator.format( "Please enter no more than {0} characters." ),

     minlength: $.validator.format( "Please enter at least {0} characters." ),

     rangelength: $.validator.format( "Please enter a value between {0} and {1} characters long." ),

     range: $.validator.format( "Please enter a value between {0} and {1}." ),

     max: $.validator.format( "Please enter a value less than or equal to {0}." ),

     min: $.validator.format( "Please enter a value greater than or equal to {0}." )

 }

 $().ready(function() {

 // 在键盘按下并释放及提交后验证提交表单

   $("#signupForm").validate({

     rules: {

       firstname: "required",

       lastname: "required",

       username: {

         required: true,

         minlength: 2

       },

       password: {

         required: true,

         minlength: 5

       },

       confirm_password: {

         required: true,

         minlength: 5,

         equalTo: "#password"

       },

       email: {

         required: true,

         email: true

       },

       topic: {

         required: "#newsletter:checked",

         minlength: 2

       },

       agree: "required"

     },

     messages: {

       firstname: "请输入您的名字",

       lastname: "请输入您的姓氏",

       username: {

         required: "请输入用户名",

         minlength: "用户名必需由两个字母组成"

       },

       password: {

         required: "请输入密码",

         minlength: "密码长度不能小于 5 个字母"

       },

       confirm_password: {

         required: "请输入密码",

         minlength: "密码长度不能小于 5 个字母",

         equalTo: "两次密码输入不一致"

       },

       email: "请输入一个正确的邮箱",

       agree: "请接受我们的声明",

       topic: "请选择两个主题"

      }

     })

 });

 <form class="cmxform" id="signupForm" method="get" action="">

   <fieldset>

     <legend>验证完整的表单</legend>

     <p>

       <label for="firstname">名字</label>

       <input id="firstname" name="firstname" type="text">

     </p>

     <p>

       <label for="lastname">姓氏</label>

       <input id="lastname" name="lastname" type="text">

     </p>

     <p>

       <label for="username">用户名</label>

       <input id="username" name="username" type="text">

     </p>

     <p>

       <label for="password">密码</label>

       <input id="password" name="password" type="password">

     </p>

     <p>

       <label for="confirm_password">验证密码</label>

       <input id="confirm_password" name="confirm_password" type="password">

     </p>

     <p>

       <label for="email">Email</label>

       <input id="email" name="email" type="email">

     </p>

     <p>

       <label for="agree">请同意我们的声明</label>

       <input type="checkbox" class="checkbox" id="agree" name="agree">

     </p>

     <p>

       <label for="newsletter">我乐意接收新信息</label>

       <input type="checkbox" class="checkbox" id="newsletter" name="newsletter">

     </p>

     <fieldset id="newsletter_topics">

       <legend>主题 (至少选择两个) - 注意：如果没有勾选“我乐意接收新信息”以下选项会隐藏，但我们这里作为演示让它可见</legend>

       <label for="topic_marketflash">

         <input type="checkbox" id="topic_marketflash" value="marketflash" name="topic">Marketflash

       </label>

       <label for="topic_fuzz">

         <input type="checkbox" id="topic_fuzz" value="fuzz" name="topic">Latest fuzz

       </label>

       <label for="topic_digester">

         <input type="checkbox" id="topic_digester" value="digester" name="topic">Mailing list digester

       </label>

       <label for="topic" class="error">Please select at least two topics you'd like to receive.</label>

     </fieldset>

     <p>

       <input class="submit" type="submit" value="提交">

     </p>

   </fieldset>

 </form>