To make sure we see the websites and photos on our display, we should properly set up our monitor.
Brightness and contrast: Set brightness and contrast to minimum, as well set everything do its default. Then slowly rise brightness till we barely see the highest number on the white scale. Repeat this with the contrast too.
Gamma: The gamma is the difference from the optimal linear imaging of the different light levels we see on the display. Raising it will raise only the light levels between the maximum and the minimum, meaning, it only influences the grey tones. With this we are able to set our display so we see the grey levels optimally, in this case, we should see the numbers on the dark scale, between 3 and 5.
The bottom left figures helps to make these settings more precisely.
Color: With the colour scales we are able to set the same settings separately to every color channels, if our monitor or software enables this. We should see every color scale the same.
Faulty cable or display: If our monitor cable or the display itself has some problems, we will see the bottom right figure has been distorted, there are shadows or repetitions or the lines.