The Dink Network

I submitted a screenshot and it was rejected.
The status message I got said it needed to be in 4x3 ratio, what does that mean?

probably means that the hight has to be 75% of the hight. e.g: 3 is 75% of 4, another example is 12x16 pixels, or something

Though more realistic examples are 640x480, 800x600 and 1024x768.

Thanks