S.B.
That spot is caused by a chemical reaction between the rubber on the rug and the linoleum. Scrubbing the floor will most likely minimize the appearance (especially if the rest of the floor is dingy), but it's a permanent mark on the linoleum. We own a rental property with linoleum in the kitchen...I have researched it thoroughly trying to get rid of stains left behind from the rugs of our previous tenants.