How to set visible=false of div element from his class name ?

You can do using jQuery. I have three steps

1. create two div one has css class and another does not have

<div class="myClass">
        It is hidden div
    </div>
    <div>
        It is visble div
    </div>

2. Add reference of jQuery library

<script type="text/javascript" src="//ajax.googleapis.com/ajax/libs/jquery/1.10.1/jquery.min.js"></script>

3. Create your function where you hide a div. I am going to hide div on first time page/document loads.

<script type ="text/javascript">
          $(document).ready(function () {
              $(".myClass").css("display", "none");
          });
      </script>