Why does the following code make the entire screen flash when either of the dropdown is clicked?
<asp:UpdatePanel ID="UpdatePanel5" runat="server" UpdateMode="Conditional"><ContentTemplate><td style="width:10%;"><asp:DropDownList ID="DropDownList1" runat="server" Width="95%" AutoPostBack="true" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged"></asp:DropDownList></td><td style="width:10%;"><asp:DropDownList ID="DropDownList2" runat="server" Width="95%" AutoPostBack="true" OnSelectedIndexChanged="DropDownList2_SelectedIndexChanged"></asp:DropDownList></td></ContentTemplate></asp:UpdatePanel>