it could be that your lcd panel is faulty, or check out your brightness or contrast settings if it doesn't help then the panel could be the problem..

I'm assuming this is a PC with external monitor. First step here, take a really bright flashlight. I use a krypton bulbed Maglight, and shine it at a 45 degree angle to the screen. If you can see the data that is supposed to be there, then the backlight is not working. If you like delicate operations, well then you have found one. Open up the unit, be carefull there is high voltage in there. If that scares you, then take it to a repair shop, if not then proceed with caution here. Take Digital Volt Ohm Meter (DVOM) and test the output of your inverter(s). If the voltage is within specs (that you looked up on the web) then your backlight is blown out. If there is no output from the inverter(s) then the inverter board has failed. If there is more than one inverter, and multiple backlights, then it is likely that the board has failed. Since you are now inside the machine, inspect the board for any funny discoloration, burn marks, or melted components. If you find any such things, replace the affected components, if you don't find any of the aforenmentioned signs, remove the board and flip it over and using at least a 5X magnafying glass inspect all the solder joints. If there are any in question, resolder them and retest the unit. If the board looks good, then look at all the other boards in the unit. There are usually 2 inside an LCD monitor. Good luck, and repost with results. And remember, THERE IS HIGH VOLTAGE stored in these boards, touching the wrong 2 terminals will knock you hard and fast. If you don't know what to stay away from, then hand it to someone who does. No offense here buddy, just a word of caution.

For starters, don't think of using a VOM to test your inverter output unless it's rated at 1000 V. Most inverters put out something in the 600 V range of impertect AC. Second, your VOM probably has a simple resistive load, not what the inverter is expecting, so you might short it out. A nonivasive test I worked out with a good VOM that measures HZ is shown here

http://www.fonerbooks/com/test.htm

Morris

yeah sounds like the Backlight or Inverter has gone (could even be both)

DO NOT open your monitor yourself. Send it away or just buy a new one.

well i would say that these kinds of problems are not commonly found in the lcd monitors so
if your lcd monitor is in warranty than you should better use and dont o experiment just reach the service center
and may the voltage you are supplying is not proper .........