textbox blur event

clientside

 <script language="javascript">

function ShowMessage()
{

alert("Message");
document.getElementById("txtidtype").value = 1;

}

    </script>

<asp:TextBox ID="txtemail" runat="server" onBlur="ShowMessage();"></asp:TextBox>

serverside:

  <asp:TextBox ID="txtidtype" runat="server" OnDataBinding="txtidtype_TextChanged"
                        AutoPostBack="True"></asp:TextBox>

protected void Page_Load(object sender, EventArgs e)
    {
     
        Response.Write("hru");
    }