Step back from your monitor.
One of these numbered boxes is about the same shade as the surrounding.
This is your "screen gamma."
Many photographer's web pages are designed for 1.8 Gamma.
"Wintel" computers and TV monitors are calibrated for 2.2 Gamma.
Windows 98, Photoshop, and Apple's Quicktime, among others, offer ways to change your
gamma, if you so desire.