Custom errors in SharePoint 2010

The previously announced postings about creating custom picker-fields are still on hold on my site, I'm deeply sorry for that. Currently I'm familiarize oneself with SharePoint 2010 and there's less time for writing large articles like the promised but it will come, I swear! ;-)

Instead of that, here comes a little hint I found while playing around with the 2010 beta. You all know how to enhance the error-logging by setting customError mode to "Off". I did this in web.config in inetpub-directory but the page still throws such an error-message:

After a little googling, I found the hint, that there's another (new) location for the web.config in C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\TEMPLATE\LAYOUTS.
There you have to set customErrors mode to "Off" as you know it and everything works fine again.