You can calibrate your screen by using a "Colour Calibration Spyder". There are many chinese manufactured ones around at the moment some are worth the money others not. Have used this one, Pantone ColorVision Spyder PRO, many times but an earlier model and it worked well. To be honest unless your doing many runs for print it is not worth your bother. Used to work in newspaper and we had to use the spyder around once a month.