To get more information from SharePoint error messages rather than just “An unexpected error has occurred”, you need to make some modifications to the web.config file of your web application.

To do so:

  1. Run IIS and explore to the root folder of your sharepoint root application.
  2. Modify the web.config file.
  3. Ctrl-F and look for the line of code that contains “callstack”.
  4. You will see a line that looks like: <SafeMode MaxControls=”200″ CallStack=”false” DirectFileDependencies=”10″ TotalFileDependencies=”50″ allowPageLevelTrace=”False”>
  5. Change CallStack and AllowPageLevelTrace to True
  6. Ctrl-F again and search for teh word “errors”
  7. You will see a line that looks like <custoErrors mode=”On” />
  8. Change this to Off
  9. Save web.config and restart IIS.

Note. It is recommend to do this only for your development environment.