Monitor Calibration

Although some photographs will reproduce quite well with less than "true color" (e.g. 256 colors), many will not..  For best viewing of pictures, set your monitor at "true color" (24-32 bit) with 800x600 screen resolution or higher.  If screen images look dark or light overall,  your monitor  may need adjustment/calibration.  See below. 

A photograph or graphic image may not be interpreted or show properly if you have a problem with your monitor  or, it is not calibrated properly.  There are a number of good references on the Internet if you require help with this.

PhotoShop for Photographers .

Accurate Image Manipulation - Timo Autiokari, 1996-2002. Espoo City, Finland.

The Denver Public Library  has a page dealing with setting the color palette,  balance, brightness and contrast.  Use the site map and follow their "help" menu to "calibrating your monitor".

PCWorld article in March 2004 issue "Calibration for Color Perfection".

There are are a number of sites that  will help you determine and adjust monitor gamma e.g.
Web Design Daily Guide
Estimating Monitor Gamma
Search (monitor gamma)

There is also information on web graphic formats (gif, jpeg and png) at
 Dan's Data
 The Apache XML Project
 and others (search "graphic formats") .

Even with your monitor calibrated, you may see images that are dark or light.  However, properly adjusting the monitor should help reduce the number of occurrences.