There are three major types of panels used in LCD. TN, VA, and IPS.
TN have the best response times, but the colors are pretty bad. These are the cheapest monitors and usually used in 22 inch variants.
VA have good colors but worse response times (recently, the response times of VA have been getting much better). Middle of the road panels.
IPS have the best response and the best color, and the best viewing angle. These can be very pricey.
Since TN panels look like utter crap in most cases, in my opinion, I usually recommend VA panels to people. Unless you can afford or need an IPS. Check out samsung panels, they use mostly VA. Usually 23-24 inch are VA. There are also a ton of other different types within each category (TN, VA, IPS) so do some more research if you're seriously considering buying a new LCD. Most people seem to think that price and size are the only things that matter, but it's important to know what type of panel you're buying too.