安装ajax.net后,部分css不起作用了,有人遇到过吗,该怎么解决

安装ajax.net后,部分css不起作用了,有人遇到过吗
vs2005 + windows server 2003 + asp.net 2.0 
没装ajax.net以前,css很正常,
安装以后,部分css不起作用了,使界面有些乱,
只要把web.config文件复原就恢复正常,
各位有知道原因的吗?

下面是我的 config文件


<?xml version="1.0"?>
<configuration>
  <configSections>
  <sectionGroup name="system.web.extensions" 

type="System.Web.Configuration.SystemWebExtensionsSectionGroup, System.Web.Extensions, 

Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35">
  <sectionGroup name="scripting" type="System.Web.Configuration.ScriptingSectionGroup, 

System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, 

PublicKeyToken=31bf3856ad364e35">
  <section name="scriptResourceHandler" 

type="System.Web.Configuration.ScriptingScriptResourceHandlerSection, System.Web.Extensions, 

Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" 

requirePermission="false" allowDefinition="MachineToApplication"/>
  <sectionGroup name="webServices" 

type="System.Web.Configuration.ScriptingWebServicesSectionGroup, System.Web.Extensions, 

Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35">
  <section name="jsonSerialization" 

type="System.Web.Configuration.ScriptingJsonSerializationSection, System.Web.Extensions, 

Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" 

requirePermission="false" allowDefinition="Everywhere" />
  <section name="profileService" 

type="System.Web.Configuration.ScriptingProfileServiceSection, System.Web.Extensions, 

Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" 

requirePermission="false" allowDefinition="MachineToApplication" />
  <section name="authenticationService" 

type="System.Web.Configuration.ScriptingAuthenticationServiceSection, System.Web.Extensions, 

Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" 

requirePermission="false" allowDefinition="MachineToApplication" />
  </sectionGroup>
  </sectionGroup>
  </sectionGroup>
  </configSections>
  
  <system.web>
  <pages>
  <controls>
  <add tagPrefix="asp" namespace="System.Web.UI" assembly="System.Web.Extensions, 

Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/>
  </controls>
  </pages>
  <!--
  Set compilation debug="true" to insert debugging
  symbols into the compiled page. Because this
  affects performance, set this value to true only
  during development.
  -->
  <compilation debug="false">
  <assemblies>
  <add assembly="System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, 

PublicKeyToken=31bf3856ad364e35"/>
  </assemblies>
  </compilation>

  <httpHandlers>
  <remove verb="*" path="*.asmx"/>
  <add verb="*" path="*.asmx" validate="false" 

type="System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions,