Untitled

jQuery( "#modalform" ).validate({
    rules: {
        chosen_domain: {
            required: true,
            minlength: 4,
            remote: "index.php?option=com_component&task=checkDomain&tmpl=component"
        }
    },
    messages: {
        chosen_domain: {
            required: "Required input",
            minlength: jQuery.validator.format("Please, at least {0} characters are necessary"),
            remote: jQuery.validator.format("{0} is already in use"),
        }
    }
});

<body class="contentpane">
    <div id="window-mainbody" class="window-mainbody">
      <div id="system-message-container">
    </div>

      "false"
    </div>
  </body>