This test card is made up of four sections. The top section is the three primary and three secondary colours: Red, Green and Blue, Yellow, Magenta and Cyan. The next section is Black through to White using the four intermediate greys in the websafe palette (the full palette is shown at the bottom of the page). The third section is a grey scale in 10% steps from black to white and the fourth section grades from Black to White in 480 steps - one step per pixel. The bottom two sections will look ‘dithered’ if your monitor is set to 256 colours (8 bit) or less, and the bottom section will look slightly ‘stepped’ in thousands of colours (16 bit).