I need a computer screen for editing photos (and playing games, but that's another story). Maximum price is around 200$. Sizewise 21-22" would be nice.
Thanks in advance,
Its hard to go wrong with Dell Ultrasharp, they are really nice displays in all sizes.
As mentioned, the preferred display for photo editing is an IPS display. It can be confusing to figure out which displays are IPS. Apple's iMac and Cinema Displays are IPS, and many Ultrasharp's are, but Dell seems to change supplier's on a whim and the technology changes as often.
As of this post, Dell claims their 27" and 30" are IPS, but no mention of what other sizes are.
I think you'll be able to find a monitor for that budget you have.
I would recommend checking Newegg.com or Fry's for prices. They always have great sales on monitors.
Be sure to review websites for reviews or google will work (although you have to take more time to filter through them).
It shouldn't matter how much just be sure to color calibrate your display and that your display is durable (as i've had a monitor die on me).
A fresh, August 2012, ranking from CNET, which includes below US$ 200 monitors: http://reviews.cnet.com/2733-3174_7-924.html