Correlation Id as follows is not the useful debug information for developer.
It is possible to use ULS Viewer to trace the log file in the background. (ULS View Download:http://www.microsoft.com/en-us/download/details.aspx?id=44020 )
In order to display the call stack of the web part, we should change the configuration in “web.config” file of the application directory ,e.g. “C:\inetpub\wwwroot\wss\VirtualDirectories\80”.
Set the attribute “CallStack” in Element “SafeMode” to “true”,
Set the attribute “mode” in Element “customErrors” to “Off”.
The better error message will be shown.