Find out if your monitor settings are correct and accurate.

I found a few web sites that help to evaluate monitors. You may be able to fine tune some adjustments on your computer monitor at a minimum.

Most calibration web sites focus on matching your monitor to the printed image coming from your printer, but the reality is that most people will be view your images online include juries, jurors, fellow artists and makers along with your collectors.

This blog post includes a guide for testing the views of white and blacks.
http://askharriete.typepad.com/ask_harriete/2011/03/monitor-madness-going-nuts.html
Be advised that the graphics card in your computer has a lot to do with the image on your monitor, but do the best you can with adjustments.