Edit in JSFiddle

$(document).ready(function() {
    $("#contact-form").validate({
        rules: {
            fullName: { //input name: fullName
                required: true,
                //required boolean: true/false
                minlength: 5,
            },
            email: { //input name: email
                required: true,
                //required boolean: true/false
                email: true //required boolean: true/false
            },
            subject: { //input name: subject
                required: true,
                //required boolean: true/false
                minlength: 5
            },
            message: { //input name: message
                required: true,
                minlength: 1
            }
        },
        messages: { //messages to appear on error
            fullName: {
                required: "Please put your full name.",
                minlength: "C'mon full name please."
            },
            email: "Enter a valid email.",
            subject: {
                required: "Whats the topic?",
                minlength: ""
            },
            message: {
                required: "What did you want to say?",
                minlength: "Please complete your thoughts, then submit."
            }
        },
        submitHandler: function(form) {
            $(form).ajaxSubmit({
                url: "echo/html",
                type: "GET",
                success: function() {
                    alert('inside');
                    $('#contact-form').hide();
                    $('#sent').show();
                }
            });
        }

    });
})

    <div id="contact" class="corner-5">
        <a class="handle" href="http://lesson8.blogspot.in/">Contact</a>
        <form id="contact-form" method="post">
            <input class="input required error" type="text" name="fullName" title="What shall I call you?" placeholder="Name"/>
            <input class="input required error" type="text" name="email" title="[email protected]" placeholder="Email Address"/>
            <input class="input required error" type="text" name="subject" title="Topic of conversation" placeholder="Title"/>
            <textarea class="txt-input required error" name="message" rows="6" placeholder="Message"></textarea>
            <input class="submit" type="submit" name="submit" value="submit"/>
        </form>
        <div id="sent">Sucess</div>
    </div>

#contact{
    padding: 20px;
    width: 250px;
    background: #FFF;
    border: 1px solid #29216d;
    position: static;
    margin-top:20px;
    margin-left:20px;
    position: fixed; 
    z-index: 200;
    -moz-box-shadow:    inset 0 0 10px #000000;
    -webkit-box-shadow: inset 0 0 10px #000000;
    box-shadow:         inset 0 0 10px #000000;
}   
.txt-input,
.input{
    color:#aaa;
    margin: 3px 0;
    font-family: Helvetica;
    font-size: 11px;
}
.txt-input{
    width: 250px;
}
.input{
    width: 200px;
}
.txt-input:focus,
.input:focus{
    color:#000;
}
label.error{
    float: left;
    font-size: 10px;
    font-weight: bold;
    color:red;
}
.submit{
    margin-top:20px;
    display: block;
    padding:5px;
}
#sent{
    display:none;
}