My samsung lcd monitor have a dim light.. i cant see most of pictures or any thing that has a dark part on it... like pictures, videos

Depends on the model. Have you checked the backlight, (LED in this set perhaps).

Back - light problem. Check and replace damaged component/s at its back-light inverter board, or replace this board as card basis. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts. It will be best to replace the inverter board as card basis.
http://electronicshelponline.blogspot.com/
To some model sets; especially LED back-lighted types; the back-light inverter circuit will be part of the main power supply board [SMPS]. In such cases, the power supply board might need replacement. To some models sets, the back-light inverter and SMPS section circuit will be integrated at its main board itself. If so; the main board should be replaced. To some models of sets, all these section circuit will be integrated at its main board. If this is the case, you have to replace the main board.

I would say either the video cable has disconneted, causeing the led that lights the screen up to not function,, simpley take the bezel around the screen, take the small screws aroud the screen to slightley pull the screen away from the back top to see if the cable is, or has pulled loose...If now the screen is bad..

Check the contrast (darkness/lightness) on your Samsung LCD. There's a menu button on the monitor, press that and select contrast setting from the Menu.

You may have a faulty inverter or defective CCFL lamp. A faulty CCFL lamp may have the following symptom: Screen flashes on and off or displays reddish pink hue. Picture stays on in red and slowly be come normal. Picture flickering and/or with dim display or appear black. Picture flickers on and off. All these symptoms indicate that the LCD backlight lamp (CCFL Lamp) has reached the end of the life and all you need to do is replace the CCFL lamp.
To determine if the video card or the LCD is faulty, connect an external monitor to your laptop and power the monitor up first then the laptop, if you see the normal Windows images then the video card and laptop is OK and the problem is definitely the backlight. Dim image and/or dark display on the laptop's LCD screen indicates a faulty LCD backlight or a faulty inverter that supplies high voltage to the CCFL lamp. Usually the CCFL lamp fails before the inverter.
The inverter can be replaced easily but the CCLF lamp is more time consuming and requires soldering skills.
Check out LCD Parts for service, parts, and DIY info Use this link to their WEB site: -
www.ladparts.net

You may have a defective CCFL backlight, it may have the following symptom: Screen flashes on and off or displays reddish pink hue. Picture stays on in red and slowly be come normal. Picture flickering with dim display or appear black. Picture flickers on and off. All these symptoms indicate that the LCD backlight lamp (CCFL Lamp) has reached the end of the life and all you need to do is replace the CCFL lamp.
To determine if the video card or the LCD is faulty, connect an external monitor to your laptop and power the monitor up first then the laptop, if you see the normal Windows images then the video card and laptop is OK and the problem is definitely the backlight. Dim image and/or dark display on the laptop's LCD screen indicates a faulty LCD backlight. It could be the inverter that supplies high voltage to the CCFL lamp or it is the CCLF lamp is nearly burnt out, this is the most likely case.
The inverter can be replaced easily but the CCLF lamp is more time consuming and requires soldering skills.
Check out LCD Parts for service, parts, and DIY info Use this link to their WEB site: -
www.lcdparts.net

You may have a faulty inverter or a faulty CCFL lamp.

A defective CCFL backlight, it may have the following symptom: Screen flashs on red/pink and off. Picture stays on in red and slowly be come normal. Picture flickering with dim display or appear black. Picture flickering on and off. All these symptoms indicate that the LCD backlight lamp (CCFL Lamp) has reached the end of the life and all you need to do is replacing the CCFL lamp.
Connect an external monitor to your laptop and power the monitor up first then the laptop, if you see the normal Windows images then the video card and laptop is OK and the problem is definitely the backlight. Dim image and/or dark display on the laptop's LCD screen indicates a faulty LCD backlight and it could be the inverter that supplies high voltage to the CCFL lamp or it is the CCLF lamp is nearly burnt out or burnt out, most likely this is the case.
The inverter can be replaced easily but the CCLF lamp is more time consuming and requires soldering skills.
Check out
www.lcdparts.net

You could have a faulty CCFL lamp or inverter, To determine if you have a LCD screen, inverter or video card problem, read this and follow these instructions.
Defective CCFL backlight, it may have the following symptom: Screen flashs on red/pink and off. Picture stays on in red and slowly be come normal. Picture flickering with dim display or appear black. Picture flickering on and off. All these symptoms indicate that the LCD backlight lamp (CCFL Lamp) has reached the end of the life and all you need to do is replacing the CCFL lamp.
Connect an external monitor to your laptop and power the monitor up first then the laptop, if you see the normal Windows images then the video card and laptop is OK and the problem is definitely the backlight. Dim image and/or dark display on the laptop's LCD screen indicates a faulty LCD backlight and it could be the inverter that supplies high voltage to the CCFL lamp or it is the CCLF lamp is nearly burnt out or burnt out, most likely this is the case.
The inverter can be replaced easily but the CCLF lamp is more time consuming and requires soldering skills.
Check out
www.lcdparts.net
for parts, repair service and DIY info.

This could be a faulty CCFL lamp.
To determine if you have a LCD screen, inverter or video card problem, read this and follow these instructions.
Defective CCFL backlight, it may have the following symptom: Screen flashs on red/pink and off. Picture stays on in red and slowly be come normal. Picture flickering with dim display or appear black. Picture flickering on and off. All these symptoms indicate that the LCD backlight lamp (CCFL Lamp) has reached the end of the life and all you need to do is replacing the CCFL lamp.
Connect an external monitor to your laptop and power the monitor up first then the laptop, if you see the normal Windows images then the video card and laptop is OK and the problem is definitely the backlight. Dim image and/or dark display on the laptop's LCD screen indicates a faulty LCD backlight and it could be the inverter that supplies high voltage to the CCFL lamp or it is the CCLF lamp is nearly burnt out or burnt out, most likely this is the case.
The inverter can be replaced easily but the CCLF lamp is more time consuming and requires soldering skills.
Check out
www.lcdparts.net
for parts, repair service and DIY info.

I had a similar problem with this monitor, mine was dim all the time to the point you cant use it, but the MENU icon was bright as new... also if cable was unplugged the box would float around as normal.... anyway I fixed it by taking it all apart and pushing in the socketed chip.. it clicked like it moved, I also pushed on the variable resistors on the power supply... now it works!!! First time since it quite working long time ago