<script src="scripts/jquery-1.6.4.js" type="text/javascript"></script> 
<script src="scripts/jquery.validate.js" type="text/javascript"></script> 

<script type="text/javascript"> 
////<![CDATA[ 
$(document).ready(function(){ 
  $("#commentForm").validate(); 
}); 
//]]> 
</script> 

class="required"  必须填写 
class="required email"    必须填写且内容符合Email格式验证 
class="url"       符合URL格式验证 
minlength="2"   最小长度为2 

<script type="text/javascript"> 
////<![CDATA[ 
$(document).ready(function(){ 
  //将$("#commentForm").validate(); 改成 
  $("#commentForm").validate({meta: "validate"}); 
}); 
//]]> 
</script> 

class="{validate:{required: true, minlength: 2, messages:{required:'请输入姓名', minlength:'请至少输入两个字符'}}}" 
class="{validate:{required: true, email: true, messages:{required:'请输入电子邮件', email:'请检查电子邮件的格式'}}}"    

$("#commentForm").validate({ 
  rules: { 
   username: { 
     required: true, 
     minlength: 2 
   }, 
   email: { 
     required: true, 
     email: true 
   }, 
   url:"url", 
   comment: "required" 
  }, 
  messages: { 
   username: { 
     required: '请输入姓名', 
     minlength: '请至少输入两个字符' 
   }, 
   email: { 
     required: '请输入电子邮件', 
     email: '请检查电子邮件的格式' 
   }, 
   url: '请检查网址的格式', 
   comment: '请输入您的评论' 
  } 
}); 

errorElement: "em",        //可以用其他标签，记住把样式也对应修改 
success: function(label) {  //label指向上面那个错误提示信息标签em 
   label.text("")            //清空错误提示消息 
       .addClass("success");  //加上自定义的success类 
   } 
在CSS中添加样式与之关联 
em.error { 
   background:url("images/unchecked.gif") no-repeat 0px 0px; 
   padding-left: 16px; 
} 
em.success { 
   background:url("images/checked.gif") no-repeat 0px 0px; 
   padding-left: 16px; 
} 

//自定义一个验证方法 
$.validator.addMethod( 
  "formula", //验证方法名称 
  function(value, element, param) {//验证规则 
    return value == eval(param); 
  },  
  '请正确输入数学公式计算后的结果'//验证提示信息 
); 
 
$("#commentForm").validate({ 
  rules: { 
   username: { 
     required: true, 
     minlength: 2 
   }, 
   email: { 
     required: true, 
     email: true 
   }, 
   url:"url", 
   comment: "required", 
   valcode: { 
     formula: "7+9" 
   } 
  }, 
  messages: { 
   username: { 
     required: '请输入姓名', 
     minlength: '请至少输入两个字符' 
   }, 
   email: { 
     required: '请输入电子邮件', 
     email: '请检查电子邮件的格式' 
   }, 
   url: '请检查网址的格式', 
   comment: '请输入您的评论', 
   valcode: '验证码错误' 
  } 
});