Beyond `web.config`, what other server-level or application pool settings in IIS could override or interfere with `customErrors mode="Off"`?

In addition to `web.config`, the following IIS settings can interfere: 1. **IIS `httpErrors` Module:** Configured in `system.webServer` (or globally in `applicationHost.config`), this module handles all HTTP status codes (e.g., 500, 404) at the IIS level, potentially overriding ASP.NET's `customErrors`. If it's configured to display a specific static page for 500 errors, that page will be shown regardless of `customErrors mode="Off"`. 2. **Failed Request Tracing:** While not an override, configuring Failed Request Tracing in IIS can help diagnose what's happening at the server level, showing if IIS is intercepting the error before ASP.NET has a chance to render it. 3. **Application Pool Identity/Permissions:** Though less direct, if the application pool's identity lacks permissions to read the `web.config` or certain resources, it could lead to generic errors that seem unrelated to `customErrors`.