Loading Image during PostBack ASP.Net Validators Problem

for validation add this script by replacing the existing one

<script type = "text/javascript">
  function ShowProgress() {
      setTimeout(function () {
          var modal = $('<div />');
          modal.addClass("modal");
          $('body').append(modal);
          var loading = $(".loading");
          loading.show();
          var top = Math.max($(window).height() / 2 - loading[0].offsetHeight / 2, 0);
          var left = Math.max($(window).width() / 2 - loading[0].offsetWidth / 2, 0);
          loading.css({ top: top, left: left });
      }, 50);
  }

  function disableBtn(btnID, newText) {

      Page_IsValid = null;

      if (typeof (Page_ClientValidate) == 'function') {
          Page_ClientValidate();
      }

      var btn = document.getElementById(btnID);
      var isValidationOk = Page_IsValid;

      if (isValidationOk !== null) {

          if (isValidationOk) {
              ShowProgress();

          }
          else {
              btn.disabled = false;
          }
      }
      else {
          setTimeout("setImage('" + btnID + "')", 10);
          btn.disabled = true;
          btn.value = newText;
      }
  }
  function setImage(btnID) {
      var btn = document.getElementById(btnID);
      btn.style.background = 'url(Images/sloading.gif)';
  }


 </script>

then in button code add

OnClientClick="disableBtn(this.id, 'Submitting...')" UseSubmitBehavior="false"

 <asp:Button ID="btnRefresh"  runat="server" Text="Refresh" CssClass="ibutton" Width="104px"
         OnClientClick="disableBtn(this.id, 'Submitting...')" UseSubmitBehavior="false" />