Is it bad for my credit rating to have credit cards and not use them?

matt asked:


I have three credit cards but only use one, and pay it off in full every month. I am planning on making a big purchase at Best Buy and can save a lot of money if I open a credit card with the purchase. (I believe like 20% which would be almost $150). I would never use that card again.

Is it bad for my credit rating to have credit cards that I never use?

Esther