<asp:TextBox ID="txtHKMonth" runat="server" CssClass="month" onkeyup="this.value=this.value.replace(/D/g,'')" onafterpaste="this.value=this.value.replace(/D/g,'')"></asp:TextBox>
<asp:TextBox ID="txtHKMonth" runat="server" CssClass="month" onkeyup="this.value=this.value.replace(/D/g,'')" onafterpaste="this.value=this.value.replace(/D/g,'')"></asp:TextBox>