I get an unexpected or runtime error but how can I get detailed error description?

To get detailed error description please follow the next steps:

   *  open IIS home directory (usually C:\inetpub)
   *  navigate to "wwwroot\wss\VirtualDirectories"
   *  navigate to appropriate folder (usualy 80 for default web application)
   *  open "web.config" file using notepad
   *  Search for: CallStack="false"
   *  Replace with: CallStack="true"
   *  Search for: customErrors mode="On"
   *  Replace with: customErrors mode="Off"
   *  Search for: debug="false"
   *  Replace with: debug="true"
   *  navigate to "C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\TEMPLATE\LAYOUTS" (...\15\TEMPLATE\LAYOUTS for SP 2013)
   *  open "web.config" file using notepad
   *  Search for: customErrors mode="On" 
   *  Replace with: customErrors mode="Off" 

Repeat it for all WFEs.

If you still get just a 'Runtime error' after that is done, make sure you also set customErrors mode="Off" in \TEMPLATE\LAYOUTS\web.config

If you still get just a 'Runtime error' after that is done, you might want to also set customErrors mode="Off"in IIS:

   * select the wanted IIS site

   * under section 'Management' click Configuration Editor

   * under 'Section' select 'system.web' folder ---> customErrors

   * under 'From' make sure it's the web.config you want

   * finally, set mode to 'Off'

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To debug REM (Registration and Enrollment Module) error you might also insert the following line into the application's site web.config (corresponding modules) section. Make this module go first in the modules list:

<add name="ErrorHandlingModule" type="Elearningforce.Sharepoint.LMS.Enrollment.Common.Error.ErrorHandlingModule, Elearningforce.Sharepoint.LMS.Enrollment, Version=1.0.0.0, Culture=neutral, PublicKeyToken=a0480eb0bc0ac42a" />