Same here on my office TFT. I manage several websites here at my
  university and playing with colors, esp. backgroundcolors, has always
  been a pain. Usually a CRT is brighter than a TFT and offers more
  contrast, so the site looks different on any Monitor/Browser/OS.

In theory, colors on the web are in the sRGB colorspace, which has a
gamma of 2.2.  2.2 corresponds to a typical CRT (when adjusted
correctly, which is not hard but fairly rare), and results in
relatively even ratios of luminosity as one steps from 0-255.

My notebook TFT (Thinkpad T30 1400x1050) has a different gamma, and I
haven't managed to calibrate it yet.  This web page is helpful for
understanding gamma and calibration, and has a helpful chart:
http://www.normankoren.com/makingfineprints1A.html

In practice, color calibration is messy, but the right thing for a
site to do is publish in sRGB, and probably avoid requiring
distinguishing of close colors (an accessibility issue anyway).


-- 
        Greg Troxel <gdt@ir.bbn.com>