500 - asp.net中web.config的内部服务器错误

Question

我正在开发一个Windows共享服务器，以下是我的web配置文件，当我添加这个我得到500内部服务器错误是什么原因？

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <appSettings>
    <add key="ValidationSettings:UnobtrusiveValidationMode" value="None" />
  </appSettings>
  <system.web>
    <sessionState mode="StateServer" cookieless="false" timeout="60"/>
    <machineKey decryptionKey="AC48DC02356AA0F4F1A2F7BCC6DA978E4EA8EB9ED51EEE60,IsolateApps"                validationKey="3C439A37FCCD52040B1FD56A8447DA2B8AB2B568EBC732017039593D86DC6BECF09B4F42972C91151CA8C856C702897C2B45D669BA15B0441BB13BC673010E99,IsolateApps" />
    <customErrors mode="Off"/>
    <compilation debug="true" targetFramework="4.0">
      <assemblies>
        <add assembly="System.Web.Extensions.Design, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
        <add assembly="System.Design, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A" />
        <add assembly="System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089" />
      </assemblies>
    </compilation>
    <httpRuntime targetFramework="4.0" />
    <pages>
      <controls>
        <add tagPrefix="cc1" assembly="AjaxControlToolkit" namespace="AjaxControlToolkit" />
      </controls>
    </pages>
  </system.web>
  <connectionStrings>
    <add name="Connection" connectionString="Data Source=199.79.xx.xx;Initial Catalog=catalog;Persist Security Info=True;User ID=user;Password=xxxxx;Connect Timeout=100" providerName="System.Data.SqlClient" />
  </connectionStrings>
</configuration>

直到前几天工作正常，但是当我将另一个网站添加到同一服务器时，几乎相同的配置会出现错误。