A properly adjusted display (monitor) is essential if you are visiting art sites, or viewing and editing your own photos.
Professionals use hardware based color calibration tools. These cost hundreds to thousands of dollars. If you use Windows and happen to have Adobe Photoshop, it includes Adobe Gamma, which you should use to calibrate your display. Mac users should use the Calibrate utility, located in the System Preferences/Displays/Color tab. It is called the Color Sync Utility in the latest OS versions. Lacking either of these, you can get reasonable results with the steps below.
Begin by making sure your display has been on for at least a a half hour, so it us warmed up and stable. This applies to both CRT (the bulky picture tube) and flat panel displays.
Set the room light level low, but not dark.
Set your computer to show the maximum number of colors it will allow. In Windows, right click the desktop and select settings. Macintosh, select system preferences, hardware. The color depth should be at least 16 bits (thousands of colors).If you can select the color temperature of your display, set it to 6500 degrees K.
Maximize this browser window. Make it fill your screen.
If you have a CRT display, set the contrast control to maximum. This control is misnamed, it actually sets maximum display luminance. Now, adjust the brightness control (actually the black point adjustment) to get a reasonable picture.
If you have a CRT display, adjust the various horizontal and vertical controls so the square below is square. Measure with marks on a piece of paper or with a ruler. It is truly amazing that many people adjust these controls to get the image to fill the screen, rather than be true and square!
With either type of display, use the brightness and the contrast to adjust so that the grey scale below shows 17 distinct bands ranging from all black to white.