Add troubleshooting tips for http endpoints

Author: georg-jung

msix-src/app-installer/troubleshoot-appinstaller-issues.md

@@ -72,10 +72,21 @@ Windows 10 applications can have framework dependencies based on the application
 
 ### Files not accessible
 
-When installing from an HTTP endpoint, it is important to verify that all files are accessible with the correct MIME type. The easiest method to verify these files is by following the links provided in the HTML page generated by Visual Studio. You must check these files:
+When installing from an HTTP endpoint, it is important to verify that all required files are accessible. The easiest method to verify this is by following the links provided in the HTML page generated by Visual Studio. You must check these files:
 
-- `.appinstaller` file, available as an `application/xml`
-- `.appx` and `.appxbundle` files, available as `application/vns.ms-appx`
+- an `.appinstaller` file, found at `Additional Links > App Installer File` on the Visual Studio generated page
+- an `.appx`, `.appxbundle`, `.misx` or `msixbundle` file, found at `Additional Links > Package Bundle` on the Visual Studio generated page
+
+> [!NOTE]
+> Depending on your configuration, there might be more than one `.appx`, `.appxbundle`, `.misx` or `msixbundle` file involved in your deployment. Ensure that all of them are accessible.
+
+### Files served with wrong MIME type
+
+When installing from an HTTP endpoint, all files are required to be served with their [correct MIME type](/windows/msix/app-installer/installing-windows10-apps-web#how-to-enable-this-on-a-webpage) in the `Content-Type` header by the webserver.
+
+### Files served without Content-Length header
+
+When installing from an HTTP endpoint, all responses need to include a correct `Content-Length` header. This includes `GET` as well as `HEAD` requests. Ensure that all of them specify their `Content-Length` correctly. Failing to do so can lead to errors like `App installation failed with error message: Appinstaller operation failed with error code 0x80072F76. Detail: Unknown error (0x80072f76)` or others.
 
 ### App installation failed with error message: The parameter is incorrect