Augusto,
I found this website very helpful when picking a monitor. Go here, and scroll to the bottom of the page and read the section called 'The Cold, Hard Facts (Specs and Techs)'.
Other than, price, these are the two most important specs for LCD screens I think. But all the other info is good to read.
Response time
Response time is measured in milliseconds. There are two parameters quantifying the response time: gray to gray and black to white. Unlike CRT, the TFT pixels stays put until they are asked to change. The gray to gray measures how fast one pixel turns from one color shade to another of the same color. The black to white measures how fast one pixel can turn to another color. Lower response time is better. This is very important when using the screen to watch video and play games, and has been one of the factors the hard core gamers consider when going from CRT to TFT. Be very careful when reading manufacturer specs on response time. Many will not indicate whether they are measuring gray to gray, or black to white. Also, there is no consistent way to measure response time, so one manufacturers 8ms will not necessarily be the same as another. Your best bet is to see the panel in question.
Contrast ratio
Contrast ratio is the difference between the brightest white and the darkest black. 500:1 means its 500 times darker then white. Higher number usually means better image and easier to read text. However, you must take into consideration that the contrast sensitivity of your eyes are about 300:1. Still, the enviroment plays a big part here and higher ratio gives more oportunity to adjust accordingly. Contrast should be adjusted in conjunction with brightness.
I would also suggest that you just post links to the ones you are considering. Looking at a screenshot of a webpage imbedded in a word document is not the best.