Ok,i wired everything like this link http://arduino.cc/en/Tutorial/LiquidCrystal
i run the example 'Hello,world' and everything was fine except the fact that the backlight doesn't work.
i must tell you that i used a 4.7K potentiometer (instead of 10K in the example) but i see that the resistor effects on the characters contrast and not on the backlight.Character contrast works properly.When i turned it all right the characters go off,when i turned all left characters go too black.
here is a foto to see my wirings as better as it's possible
From left to right,the wires are:
LCD GND to pot and from there to arduino GND (black wire)
LCD Vcc to pot and from there,to arduino Vcc (red wire)
LCD Vo to pot (brown wire)
LCD RS to digital pin 7 (black wires for all the others)
LCD RW to pot GND
LCD Enable to digital pin 6
LCD D4 to digital pin 5
LCD D5 to digital pin 4
LCD D6 to digital pin 3
LCD D7 to digital pin 2
another photo of the connections on the potentiometer
i hope you can see clearly...
the red wire on the pot is from LCD Vcc.The other red wire goes to arduino Vcc
the brown wire is the LCD Vo
the three black wires are 1) LCD GND 2)LCD RW 3)To arduino GND
I can't have clear picture from the digital pins on arduino board,but trust me they are wired fine and correctly.