HTTP Error 500.19 - Internal Server Error after migration iis6 to iis7

I keep getting this error when open a website.

<fieldset>
HTTP Error 500.19 - Internal Server Error
The requested page cannot be accessed because the related configuration data for the page is invalid.
</fieldset>
<fieldset><legend>Detailed Error Information</legend>
Module  IIS Web Core
Notification    BeginRequest
Handler     Not yet determined
Error Code  0x80070032
Config Error    The configuration section 'connectionStrings' cannot be read because it is missing a section declaration
Config File     \\?\C:\inetpub\wwwroot\CM_Live\web.config
Requested URL   http://localhost:80/CM_Live
Physical Path   C:\inetpub\wwwroot\CM_Live
Logon Method    Not yet determined
Logon User  Not yet determined
</fieldset>
<fieldset><legend>Config Source</legend>

   22:  </configSections>
   23:  <connectionStrings>
   24:      <add name="DWG_ConnectionString" connectionString="Data Source=server;Initial Catalog=Data_;Integrated Security=True" providerName="System.Data.SqlClient"/>

</fieldset>

I google the error and read other site with people with same error but they solution didn't work for me.