Postback not working in production server - IE 11

I am using .net 4.0 . Please see this following code

 <asp:DropDownList ID="ddlCountry" runat="server" CssClass="input-xlarge" OnSelectedIndexChanged="CountrySelection_Changed" AutoPostBack="true" ></asp:DropDownList> 

Any type of post back not working like as click on button or linkbutton on production server.

This working fine all browser in production & local server except IE 11. How can solve this? Thanks in Advance!!