$().ready(function() {
    $("#loginform").validate({
 /*   errorPlacement: function(error, element) {
            error.appendTo( element.parent("td").next("td") );
                },
   */     rules: {
            username: {
                required: true
            },
            pass: {
                required: true
            }
        },
        messages: {
            username: {
                required: "Este campo no puede estar vacío"
            },
            pass: {
                required: "Introduce tu contraseña"
            }
        }
    });
});