i am also have the same trouble...
Have you got your contrast pot hooked up? If it's hooked up correctly, you should see an effect when you turn it even if nothing is displayed. If that's working, try resetting the Arduino a time or two. If it still doesn't work, I'd suggest redoing rather than just checking your wiring. Make sure you hook up all the grounds, and make sure they have a good connection. Also, it wouldn't hurt to post a picture, schematic, or listing of your pin connections (for example, are you sure pin 11 on the Arduino is hooked to the enable pin on your LCD?).
i tried what u suggest but i did not work , so i uploaded the image. if u find any mistake in wiring pls make me know.
Well, it looks like all of the pins go to the right places. Does the screen light up when you power it on? Do you see one line blacked out and the other not? What happens when you sweep the pot from one extreme to the other? Sometimes on my breadboard I have to wiggle the wires some to get a good connection, especially the grounds.
only the back light LED glow.there is no other change in display when i sweep the port.
I just tried my LCD to see what happens. If the LCD and backlight are powered, the contrast pot doesn't do anything and the display is just blank (exactly what yours is doing). I suppose that means that the Arduino isn't communicating with it properly. Can you post your setup code? Maybe try wiring it to different pins just to see what happens (it could be that, say, the ENABLE and RS are swapped). Are the pins marked on the LCD board?