vs2010中aspx源码中“[”符号什么作用？

<asp:LoginView ID="HeadLoginView" runat="server" EnableViewState="false">
                    <AnonymousTemplate>
                        [ <a href="~/Account/Login.aspx" ID="HeadLoginStatus" runat="server">Log In</a> ]
                    </AnonymousTemplate>
                    <LoggedInTemplate>
                        Welcome <span class="bold"><asp:LoginName ID="HeadLoginName" runat="server" /></span>!
                        [ <asp:LoginStatus ID="HeadLoginStatus" runat="server" LogoutAction="Redirect" LogoutText="Log Out" LogoutPageUrl="~/"/> ]
                    </LoggedInTemplate>
                </asp:LoginView>[]符号是干什么用的？