For best results, the following test should not be done in a sunlit room.
And don't worry, the test has no permanent effect.
1) Open the following image in your browser, preferrably fullscreen or near-fullscreen, or download it and open it with an image viewer. It should just fill at least most of the screen, with no shiny whites around it.
Do you notice anything already?
2) Do the same with the following picture and leave it on screen for at least 5 minutes, better 15 or more, with the symbol more or less centered. (Ideally when you're not at the PC - no reason to idle in front of the computer.)
Now open the first image again.
See what I mean?
This can be problematic for certain graphical applications where accurate display is important.