How to display error messages and the stack trace on the screen in SharePoint

You will need to make alterations to the web.config file usually located at C:\inetpub\wwwroot\wss\VirtualDirectories

NOTE: To help you find the location of the web.config file if its not in the location above you can open server manager -> IIS Manager -> Sites then right click on the site and select explore.

First turn off custom errors:

Second turn on stack trace:

Third, enable debugging:

Finally, enable tracing:

Make sure this is only done in you DEV environment as this will display config and security info to people browsing the site, it will also effect performance of your SharePoint site.