下面是我的web.config全文，中部标兰处是按你给的代码写的，只作了不关紧要的修改，但达不到你说的目标：
A,匿名可访问
B.不让匿名访问,但任何通过Form验证的角户皆可访问
C,只允许"Admin角色"的已登录用户访问，不让匿名和非“Admin角色”的已登录者访问
我在一个页面上放了指向这三个文件夹中的连接，在不登录的情况下，A和B夹中的网页可随意打开，只有C中的打不开
<?xml version="1.0"?>
<!--
注意: 除了手动编辑此文件以外，您还可以使用 Web 管理工具来
配置应用程序的设置。
可以使用 Visual Studio 中的“网站”->“Asp.Net 配置”选项。
设置和注释的完整列表在 machine.config.comments 中，
该文件通常位于
\Windows\Microsoft.Net\Framework\v2.x\Config 中
-->
<configuration>
<configSections>
<sectionGroup name="system.web.extensions" type="System.Web.Configuration.SystemWebExtensionsSectionGroup, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35">
<sectionGroup name="scripting" type="System.Web.Configuration.ScriptingSectionGroup, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35">
<section name="scriptResourceHandler" type="System.Web.Configuration.ScriptingScriptResourceHandlerSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="MachineToApplication"/>
<sectionGroup name="webServices" type="System.Web.Configuration.ScriptingWebServicesSectionGroup, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35">
<section name="jsonSerialization" type="System.Web.Configuration.ScriptingJsonSerializationSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="Everywhere"/>
<section name="profileService" type="System.Web.Configuration.ScriptingProfileServiceSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="MachineToApplication"/>
<section name="authenticationService" type="System.Web.Configuration.ScriptingAuthenticationServiceSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="MachineToApplication"/>
<section name="roleService" type="System.Web.Configuration.ScriptingRoleServiceSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="MachineToApplication"/>
</sectionGroup>
</sectionGroup>
</sectionGroup>
</configSections>
<appSettings/>
<connectionStrings>
<add name="kaoheConnectionString" connectionString="Data Source=SL-PC\SQLEXPRESS2005;Initial Catalog=kaohe;Persist Security Info=True;User ID=sa;Password=nevertell" providerName="System.Data.SqlClient"/>
</connectionStrings>
<!--以下是我写的-->
<system.web>
<authentication mode="Forms">
<forms name=".ASPNETAUTH" protection="None" timeout="20" />
</authentication>
<authorization>
<deny users="?"/>
</authorization>
<compilation debug="true">
<assemblies>
<add assembly="System.Core, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>
<add assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
<add assembly="System.Data.DataSetExtensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>