+### Serial device is not detected in bootloader mode on Linux
+Make sure your kernel has appropriate support for your device. If your device uses USB ACM, such as
+Pro Micro (Atmega32u4), make sure to include `CONFIG_USB_ACM=y`. Other devices may require `USB_SERIAL` and any of its sub options.
+
+## Unknown Device for DFU Bootloader
+
+If you're using Windows to flash your keyboard, and you are running into issues, check the Device Manager. If you see an "Unknown Device" when the keyboard is in "bootloader mode", then you may have a driver issue.
+
+Re-running the installation script for MSYS2 may help (eg run `./util/qmk_install.sh` from MSYS2/WSL) or reinstalling the QMK Toolbox may fix the issue.
+
+If that doesn't work, then you may need to grab the [Zadig Utility](https://zadig.akeo.ie/). Download this, find the device in question, and select the `WinUS(libusb-1.0)` option, and hit "Reinstall driver". Once you've done that, try flashing your board, again.
+
+## WINAVR is Obsolete
+It is no longer recommended and may cause some problem.
+See [TMK Issue #99](https://github.com/tmk/tmk_keyboard/issues/99).
+
+## USB VID and PID
+You can use any ID you want with editing `config.h`. Using any presumably unused ID will be no problem in fact except for very low chance of collision with other product.
+
+Most boards in QMK use `0xFEED` as the vendor ID. You should look through other keyboards to make sure you pick a unique Product ID.