<div class="input-group custom-search-form">
                              <form action="/search" id="form-search" method=POST>
                              <input type="text" name="query" class="form-control" placeholder="Search Paste">
                              <span class="input-group-btn">
                              <button class="btn btn-default" type="submit">
                                  <i class="fa fa-search"></i>
                              </button>
                              <img id="loading-gif" src="{{url_for('static', filename='image/loading.gif') }}" height="26" width="26" style="margin: 4px; visibility: hidden;">
                              </form>
                          </span>
                          </div>
                          <script> 
                              $("#form-search").submit(function( event ) {
                                  $("#loading-gif").css("visibility", "visible");
                              });
                          </script>