Hi all, i connected my 16x2 lcd to my arduino and everythi g worked fine... I later tried towire up the back light according to specs,really simple ,its impossible i did somethin wrong... Then when i powered everything up, i saw no back light, i justa saw many missing pixels.. I removed the back light wires, i oowerd againeverything up, some pjxels were flashing, some others missing..really crazy things.. After a while some pixels recovered, except one vertical line.. At first i thought that pixels got burnt, but then some recovered,really strange.. Any ideas..please help... ????
Check the connection between PCB and glass.
These LCD's consist of at least 2 parts: a PCB holding the driver and memory chips, and the glass holding the actual crystals.
They are connected by rubberlike bands, which has conducting lines in it.
These bands are pressed between PCB and glass by the bezel holding the glass.
This bezel again is held to the PCB by some tabs, bent over the PCB.
You can try to tighten the connection by bending those tabs a bit more.
But first try to see if there is a chance of this helping.
While in use, gently press the top of the bezel a bit.
Work your way around the entire bezel, touching one place at the time.
You will get that also with wrong code or a bad connection of a wire or a low voltage.
Did you use a resistor for the backlight ?
Did you use the usb bus to power it all ?
Perhaps you use a low value resistor and the current of the backlight lowers the 5V. Those lcd displays need a good steady 5.0V.
Those lcd displays are cheap, it could get broken just by itself. Don't spend a lot of time on this one, just buy a new one.
MAS3:
Check the connection between PCB and glass.
These LCD's consist of at least 2 parts: a PCB holding the driver and memory chips, and the glass holding the actual crystals.
They are connected by rubberlike bands, which has conducting lines in it.
These bands are pressed between PCB and glass by the bezel holding the glass.
This bezel again is held to the PCB by some tabs, bent over the PCB.
You can try to tighten the connection by bending those tabs a bit more.
But first try to see if there is a chance of this helping.
While in use, gently press the top of the bezel a bit.
Work your way around the entire bezel, touching one place at the time.
You are right, there's something wrong between the connection of those two parts.However i couldn't fix it really good so im gonna buy a new one. it was cheap anyway 
I still can't understand how it happened !!! 
im gonna buy a new one. it was cheap anyway ... I still can't understand how it happened !!
Try to find one that is inexpensive but not cheap.
Don
floresta:
im gonna buy a new one. it was cheap anyway ... I still can't understand how it happened !!
Try to find one that is inexpensive but not cheap.
Don
it was this one :Standard LCD 16x2 + extras [white on blue] : ID 181 : Adafruit Industries, Unique & fun DIY electronics and kits
Ouch !
That's not inexpensive and not cheap..
I guess these displays really aren't that different to each other.
MAS3:
Ouch !That's not inexpensive and not cheap..
I guess these displays really aren't that different to each other.
Is it a good choice?
I think this is what floresta was hinting to (can't speak in his name of course).
Adafruit is a very respected source of Arduino related hardware.
They offer very good support for their products, which can also be used for similar products from other sources that do not offer any support at all.
But still, all these products are 'defectable'.
As you didn't mention the source before, assuming you got it from the cheapest one anybody could find could turn out to be a mistake.
I think in general, Adafruit is considered to be a good choice over here at Arduino.
I understand why and agree, but have never ordered anything there myself.