jQuery-表单验证，将CSS样式添加到错误消息

我试图将CSS样式添加到使用Jquery验证显示的错误消息中。这些都在消息下。我是刚接触Jquery的人，尝试将CS​​S类添加到错误消息中没有任何效果。

HTML表格

<form method="post" action="mail.php" id="contact-form">
                   <div class="form-group">
                    <label for="name">Name</label>
                    <input type="Text" class="form-control" name="name" id="name" placeholder="Enter Name">
                  </div>
                  <div class="form-group">
                    <label for="subject">Subject</label>
                    <input type="text" class="form-control" name="subject" id="subject" placeholder="Enter Subject">
                  </div>
                  <div class="form-group">
                    <label for="email">Email address</label>
                    <input type="email" class="form-control" name="email" id="email" placeholder="Enter Email">
                  </div>
                  <div class="form-group">
                    <label for="comment">Message</label>
                    <input type="text" class="form-control" name="comment" id="comment" placeholder="Enter Message">
                  </div> 

                  <button type="submit" value="submit"  name="submit" class="btn btn-default">Submit</button>
                </form>

jQuery的

    <script type="text/javascript">
                 $('#contact-form').submit(function () {
                 $('#loadingimage').show();
                 $('#loadingtext').show();
                });
    </script>

    <script type="text/javascript">
        (function($,W,D)
        {
            var JQUERY4U = {};

            JQUERY4U.UTIL =
            {
                setupFormValidation: function()
                {
                    //form validation rules
                    $("#contact-form").validate({
                        rules: {
                            name: "required",
                            subject: "required",
                            email: {
                                required: true,
                                email: true
                            },
                            comment: "required"
                        },
                        messages: {
                            name: "Please enter your Name",
                            subject: "Please enter a Subject",
                            email: "Please enter a valid Email Address",
                            comment: "Please enter your Message",

                        },
                        submitHandler: function(form) {
                            form.submit();
                        }
                    });
                }
            }

            //when the dom has loaded setup form validation rules
            $(D).ready(function($) {
                JQUERY4U.UTIL.setupFormValidation();
            });

        })(jQuery, window, document);
        </script>