Eclipse95, getting a new monitor will not help if it's not the root of your problem. To really get a good answer you need to list your system specs including current monitor resolution, CPU, graphics card(s) and what game(s) you are playing.
For example: If you are using a GeForce 8400 card trying to play Metro 2033, then your problem is hardware.
If you are having a problem with framerates or tearing, then it is likely your video card in the computer, not the monitor. If you are having a problem with refresh rates or refresh response time, then maybe you have a very old LCD or something. Newer LCDs will not cause any LAG. It is usually the video card or CPU.
What are your system specs?
What resolution is your screen (1024x768 or 1920x1080)
What is your refresh rate? 50/59/60/70/75 Hz?
What is the model of your current monitor as well?
What is your operating system and what games or software is the lag occurring in?
Please be very specific so we can give you a more specific answer.
Currently I have no problem with my gaming by Samsung SyncMaster 151s LCD, but I'd like to buy a new monitor because my LCD is broken. I worry about if I buy the wrong monitor will cause the fps of my game decrease a little bit.
I don't think it will cause you to lose fps. If you are running the GT120 and the games at highest setting, that is your problem, not the LCD. If you get a standard LCD with a 60 or 75 Hz refresh rate, and your games fps is already higher than that, you wouldn't notice anyways... the human eye can't keep up over those refresh rates anyways. If your games are lagging, tone down the settings a bit or change the resolution. I still run a 9800Gt in my q8300 system... I turn off AA and set the resolution to 1280x720p or 1600x900 for most games and the quality settings are still on high and most games are over 60fps anyways. Even if your game and GPU can achieve 120 fps, a standard LCD can't refresh more than 60 fps anyways.
Also, sometimes when using the d-sub connector at high resolutions, you may get tearing, but switching to DVI will usually fix it.
In your case the LCD has nothing to do with lag. Either tone down the resolution and turn of AA, or change your video card.
I personally, wouldn't buy any LCD that doesn't support 1080p. Look for at least 1920x1080p... if you buy a 21" or higher that is 1366x768 or 1440x900 then you are wasting your money. Also LED is brighter and thinner, and uses less electric. You should also try to make sure it has a good contrast ratio. At least 5000:1 or more. That will give you deeper blacks and crisper images.
Also as we were stating above, your GPU would cause your lag issues, not the monitor. If you keep your current GPU, just tone the gaming resolution down to 1600x900 or 1280x720 and turn off AA. You can still play on higher settings this way. But if you want maximum resolution with AA and highest effects, it is time to change your graphics card and overclock your CPU.
LED backlight is a little bluish compared to traditional CCFL backlight (florescent). Some people may notice it others may not. LED light is below the normal color gamut of 72%; LED light has a color gamut of 68%. That means the color space is narrower than normal color gamut and is a bit "heavy" on the blue spectrum.
LED (a.k.a. WLED) does not actually produce white light. They produce yellow light, but the diode is coated with blue pigment. This is why LED light looks slightly bluish to some people.
I suggest people stick with home premium. (HP) While the other higher versions come with things like bitlocker, etc, these same things can be achieved with free programs. So unless your running a domain server at your house HP is all you need.