How do I enable .NET to show more detailed error messages on IIS 6.0?

By default, our Windows hosting servers
display a generic error when any .NET application generates an
exception. We display a generic error because the detailed error
messages allow a malicious user to obtain sensitive information.

To troubleshoot the error, you can modify your web.config file
and specify that a custom error message displays. A custom error
message helps you to locate the specific code that is causing the
issue.

CAUTION: The code samples we provide below do not constitute a
complete web.config file. Do not replace your existing web.config file
with the code we provide. Before changing your web.config file, we
recommend creating a backup.

Use the sample code below to display custom error messages on IIS 6:

<configuration>
    <system.web>
        <customErrors mode="Off"/>
        <compilation debug="true"/>
    </system.web>
</configuration>