(AP) — Wal-Mart Stores Inc. reported its fiscal third-quarter earnings slipped 1.5 percent but it eked out its first gain in nearly two years in a key revenue measure for its U.S. business. The world's largest retailer, however, issued a fourth-quarter profit outlook that missed Wall Street expectations because of expected fierce holiday discounting. Wal-Mart faces challenges on many fronts, from a slowly recovering economy that hasn't benefited its low-income shoppers and fierce competition from online king Amazon.com, dollar stores and grocers. To win its share of its holiday dollars, Wal-Mart announced an aggressive holiday plan that includes free shipping on the top 100 items and price cuts on 20,000 items. Wal-Mart's U.S.