点击按钮在Firefox中不起作用

Question

代码在Chrome中成功运行，但在Firefox中无效。

<div class=" form-group text-center">
  <div class="row">
    <div class="col-lg-offset-2 col-sm-4">
      <img src="model/capcha.php" id="capImage"/>
    </div>
    <div class="col-sm-1">
      <input name="captcha_code" type="text" value="">
    </div>
  </div>
  <button type="button" id="refreshbtn" >Click Here refresh</button>.
</div>
<script>
  $('#refreshbtn').click(function () {
    $('#capImage').attr('src','model/capcha.php');
  });
</script>