SharePoint 2010: The current custom error settings for this application prevent the details of the application error from being viewed.

Howdy, people
I have started working with SharePoint 2010.
Here is the first catch :
After the migration you have some errors on your site, but the error page just simple says:

The current custom error settings for this application prevent the details of the application error from being viewed.

And you know that you already tweaked you web.config for the application and set:

1. Debug=”true” instead of the default of Debug=”false”
2. CallStack=”true” instead of the default of CallStack=”false”
3. CustomErrors=”Off” instead of the default of CustomErrors=”On” 

What's up with that?
   SharePoint 2010 has an additional web.config under
{System Disk}:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\TEMPLATE\LAYOUTS\web.config

 Set      <customErrors mode="Off" />  there.

Now, you are happy and looking forward to encounter the fabulous error in its full glory)