$(document).ready(function() {

    var validator = $("#loginForm").validate({
        rules: {
            username: "required",
            password: "required"
        },

        errorClass: "missing",

        // Customizes where the error messages are put.
        // With an empty function, error messages are not displayed.
        errorPlacement: function() {}
    });

    $('#loginForm').keypress(function(event) {
        if (event.keyCode == 13) {
            $('#loginForm').submit();
        }
    });

    $('#loginButton').click(function() {
        $('#loginForm').submit();
        return false;
    });

});