There are some things that can-and should-be done to plastic laminate countertops. As convenient as they are, laminate countertops are susceptible to stains. Regular everyday stains can be absorbed by wiping with a damp brush or rag with some mild detergent. Stronger stains such as ink and dyes can be removed using a soft rag and alcohol or bleach.
It is important to use a soft rag or brush; an abrasive rag or brush will scour the surface. It is also important to keep the surface edges as dry as possible. If moisture gets under the edges, the laminate will pull back from the countertop. If this happens, apply more contact cement and glue the plastic back into place.