Javascript Error

Question

Label is displaying message but it is displaying for some seconds.

<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">
  <script type="text/javascript">
  function checklabel() {
  var a="Hi how r u";
  document.getElementById("<%=lbldisplay.ClientID%>").innerHTML = a;
  }
  </script>
  <asp:Label ID="lbldisplay" runat="server"></asp:Label>
  <br />
  <asp:Button ID="btnsubmit" runat="server" Text="Submit" OnClientClick="checklabel();" />
</asp:Content>
please help thanq.