My custom error page isn't displaying in IIS. What are the common reasons and troubleshooting steps?

Common reasons a custom error page might not display include: 1. **Incorrect Path**: The path to your custom error page in IIS Manager might be wrong. 2. **Permissions**: The application pool identity might lack read access to the custom error page file or its directory. 3. **`httpErrors` Configuration**: Ensure the `system.webServer/httpErrors` section in `web.config` doesn't have `errorMode` set to `Detailed` or `Off`, overriding your custom settings. 4. **`customErrors` for ASP.NET**: For ASP.NET applications, the `system.web/customErrors` section might be configured and taking precedence for application-level errors. 5. **Remote vs. Local**: IIS defaults to showing detailed errors locally but custom errors remotely (`DetailedLocalOnly`). Test from a remote machine. 6. **Error in Error Page**: The custom error page itself might have an error, causing a recursive issue.