If you hate those generic general or unspecified error or unknown error occurred or even errors that failed and told you to contact the admin without telling you why you should contact your administrator? I really hate it when I am the administrator and it tells me nothing! Well you can turn on verbose errors that actually tell you something.
The web.config calls the application default as custom errors. It may seem counter intuitive to say "turn custom errors off," but essentially you’re saying those friendly errors aren’t telling me what I need. Here’s three simple steps…
1) During your maintenance window, find in your web.config file in the <SharePoint><SafeMode> section the following line <customErrors mode="On"/> and simply change the "On" to "Off" (case sensitive).
2) Then look for Callstack="False" and change it to "True" (again case sensitive) this will actually give you the verbose (rich) details beyond the simple error codes.
3) Reset the affected app pool or app pools (or run iisreset on the command line if you’re lazy or have no idea what I’m talking about…)
I know I’m not the first to say this, but I want to make sure this is more broadly understood. This is a great troubleshooting tip. Note it will require an app pool cycle to get this to take effect since the change is in the web.config file.
Also to note, if this is on the intranet and not exposed to external users you may find keeping the errors verbose reduces troubleshooting time. I can’t argue with that. I caution for Internet sites for revealing too much detail.
Looking for more detail on this? Andrew Connell one of my favorite MVPs, has a developers quick post of making sense of SharePoint errors on this. This is obviously not new, but often not well understood that you can even do this. (Also, kudos to Shane Young for calling this out in SharePoint Survival Admin Class).