Netflix plans to stop selling DVDs that were rented by subscribers, another step toward expanding its subscription focus from DVDs rented by mail to include movies streamed over the Web.

In a Netflix blog posting Monday, the company announced that it would discontinue sales previously viewed DVDs on November 30:

“As you know, our core business is delivering great movie rentals to you on DVD by mail and instantly to the computer and TV, so we’ve decided it makes sense for us to focus exclusively on that. This means we will stop selling previously viewed DVDs through the Web site. We’re sorry for any inconvenience for those of you who regularly purchase DVDs at Netflix, but we’re excited about being able to spend the extra time focusing on continually improving our core rental business for you. ”

Netflix announced on Friday that it had completed its first phase of beta testing of its new “Watch Instantly” movie-streaming player and was expanding access to include Macintosh-owning subscribers.