Update Panels are not preventing full post backs

I'm wondering if somebody can tell me why I am still getting a full postback when a linkbutton is clicked. Here's my ASP code:
<asp:UpdatePanel ID="NewsUP" runat="server" UpdateMode="Conditional"> <Triggers><asp:AsyncPostBackTrigger ControlID="ExpandNewsLB" EventName="Click" /></Triggers> <ContentTemplate> <a id="News"></a> <div id="BlogDiv" runat="server" class="large-8 columns panel" data-equalizer-watch> <asp:Label ID="NewsTitleLb" runat="server" Text="NEWS (TOP 2)"></asp:Label> <asp:LinkButton ID="ExpandNewsLB" CssClass="fa fa-plus" runat="server" PostBackUrl="#News" EventName="ExpandNewsLB"> ...