Q:

Runtime-Error on productive Server but not locally

so i finished one of my ASP.NET-projects and want to deploy it on the productive server. And suddenly WHOOM: Runtime error!
Okay, no problem; look at the error message, see the stack trace, solve problem, everybody happy. Peanuts!
The server tells me, that the customErrors-Settings in my web.config are set that no error messages are displayed. So I take a look at the file and what do I see? <customErrors mode="Off" />.
I tried to change hat to On, RemoteOnly and whatever else. Nothing changed. How come the server doesn't recognize the setting correctly, as when I Debug the pages in VS'08 everything works perfectly fine...

A:

Make sure the IIS application is using the correct version of ASP.NET - sometimes it will default to 1.1.
In IIS6, right-click on the website or virtual directory and go to properties > ASP.NET tab. It will have a drop-down to select which version of .NET to use.
For IIS7, follow the instructions here.

