You need to check the error logs for a NetCommunity website. For example, perhaps the site is returning a runtime error and you want to know the details of the runtime error.
Alternatively, you setup a Custom Error Page and it is returning an Error ID and you want to know the details of the error ID.
If the NetCommunity Web Components are hosted by your organization, please contact your IT department to request they pull the error logs via SQL. Below is a sample Select Statement which can be shared with your IT department to assist with pulling these logs:
Select * from dbo.error where CreateDate > 'InsertDateHere'