This is Viola tricolor, the "wild" pansy:
And so is this, with less yellow:
These are hybrids, developed for size and different colors:
Pansies will always, to the best of my knowledge, show the same petal arrangement of two petals above three petals. They are known for their markings, referred to as "faces", although some of the hybrids lack the markings.
Are these the flowers you mean when you speak of pansies?
"Isn't it enough to see that a garden is beautiful without having to believe that there are fairies at the bottom of it too?" - Douglas Adams