Different grinding size for boil coffee and coffee maker? Is there any significant difference between the ideal grinding size for a drip coffee maker and for immersion (boiled) coffee?

When whole beans is not an alternative in a store, you often have the choice between coffee ground for a drip coffee maker, and for immersion (boiled) coffee. Is grind size then important?
Yes.  For a drip coffee maker, most people will want to use a medium grind that balances getting enough extraction and still allowing the water to flow through the coffee grounds.  For immersion (boiled) coffee, you generally want a course grind that will slow extraction somewhat (reduce the chance of over extraction) and make the grounds less likely to end up in the final product.