The internet is not the best way to view pictures.  All monitors display colors differently, and without proper calibration usually involving special hardware, it's difficult to set the monitor up perfectly by eye. As a result, what you see on your screen is not always what you get in print, and the print is usually better looking and more accurate than what an un-calibrated monitor displays.

There are several applications available, both freeware and commercial that help with monitor calibration.  Without going into extensive procedures here, this site can be best viewed if you can make the following grid look as neutral as possible, and still be able to make out all  of the different patches. 

Please note that this procedure is not considered highly accurate and is not a perfect substitute for proper calibration using specialized hardware.  It is only intended to get your display as close as possible to optimal viewing conditions without investing in expensive hardware.

1.  First, adjust screen contrast to maximum, then reduce it until you can see a difference between the left most, whitest blocks, on the scale.

2. Then, adjust the brightness until you see a difference between the right most, darkest blocks, on the scale.  The black block (farthest right) should be as black as possible.

3.  Finally, look for any blue, green or red color cast in the white and grey blocks.  Adjusting these usually means careful tweaking using the Red, Green and Blue controls on your monitor, if it has them. 

For more information you can visit the following sites for techniques and tools for manually calibrating your monitor:

Note that PC monitors are usually calibrated to a Gamma of 2.2 (not 2.5!) and Macs at 1.8

http://www.hex2bit.com/products/product_mcw.asp
http://www.aim-dtp.net/aim/calibration/index.htm
http://www.aim-dtp.net/aim/evaluation/gamma_space/index.htm
http://epaperpress.com/monitorcal/
http://www.normankoren.com/makingfineprints1A.html