Dampen the counter top and sprinkle some good ol' baking soda (sodium bicarbonate) on the stain, just enough to cover it. With a little elbow grease, the stain will vanish.
Source: Baking soda is great for so many things - from being a natural tooth paste, to natural deodorant, and stainless steel sink shiner!
This is a page about repairing marks on porcelain countertop. A porcelain finish can get marked and scratched. Removing or covering these blemishes can help it look better.
