各位大哥，帮我看看这个配置文件 compilers显示无效错误

<?xml version="1.0"?>
<configuration>
<configSections>
<section name="RewriterConfig" type="URLRewriter.Config.RewriterConfigSerializerSectionHandler, URLRewriter"/>
</configSections>
<connectionStrings>
  <add name="db_BlogConnectionString" connectionString="Data Source=.;Initial Catalog=db_Blog;User ID=sa"
   providerName="System.Data.SqlClient" />
  <add name="db_BlogConnectionString2" connectionString="Data Source=.;Initial Catalog=db_Blog;User ID=sa"
   providerName="System.Data.SqlClient" />
 </connectionStrings>
 <appSettings>

    <add key="conStr" value="Server=(local);DataBase=db_Blog;uid=sa;pwd="/>
</appSettings>
<RewriterConfig>
<Rules>
<!-- Rules for Blog Content Displayer -->
<RewriterRule>
<LookFor>~/(\d+)\.aspx</LookFor>
<SendTo>~/ST_show.aspx?id=$1</SendTo>
</RewriterRule>
      <RewriterRule>
        <LookFor>~/BlogIndex_(.*)_(\d+)\.aspx</LookFor>
        <SendTo>~/BlogIndex.aspx?c_id=$2&amp;name=$1</SendTo>
      </RewriterRule>
      <RewriterRule>
        <LookFor>~/BlogIndex_(.*)\.aspx</LookFor>
        <SendTo>~/BlogIndex.aspx?name=$1</SendTo>
      </RewriterRule>
</Rules>
</RewriterConfig>
<system.web>
<httpModules>
<add type="URLRewriter.ModuleRewriter, URLRewriter" name="ModuleRewriter"/>
</httpModules>
<!--
<httpHandlers>
   <add verb="*" path="*.aspx" 
        type="URLRewriter.RewriterFactoryHandler, URLRewriter" />
</httpHandlers>
--> <compilation defaultLanguage="c#" debug="true">
<compilers>
<compiler language="c#" type="Microsoft.CSharp.CSharpCodeProvider, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089" extension=".cs" compilerOptions="/d:DEBUG;TRACE"/></compilers></compilation> <customErrors mode="Off"/>
    --> <trace enabled="false" requestLimit="10" pageOutput="false" traceMode="SortByTime" localOnly="true"/>
<sessionState mode="InProc" stateConnectionString="tcpip=127.0.0.1:42424" sqlConnectionString="data source=127.0.0.1;user id=sa;password=" cookieless="false" timeout="20"/>

<globalization requestEncoding="utf-8" responseEncoding="utf-8"/>
<xhtmlConformance mode="Legacy"/></system.web>
</configuration>
<compilers></compilers>显示无效错误  怎么改