*** User can set LCD's pin 1 to GND or VCC with Jumper P3 and LCD's pin 2 to GND or VCC with Jumper P4, So please make sure that you had set the right jumper pins before turn on the arduino or else your LCD module will be destroy permanently.
*** Do NOT set Backlight variable resister to 0 ohm because arduino board's current might damage LCD's LED backlight.