The U.S. Postal Service is warning customers about temporary delays as it implements new operating practices. Starting Friday, spokeswoman Kim Frum said new standards will impact first class mail and periodicals. Frum says the changes will result in longer transit times for cross-country and other long-distance deliveries. However, single-piece first class mail that is smaller and lightweight will still have the standard two-day delivery time. Frum also mentioned a temporary holiday price increase on all commercial and retail domestic packages starting next month through Christmas.