Stocks held modest gains in afternoon trading Thursday. The Nasdaq posted a 0.4% rise. The composite owed some of its advance to Cisco Systems (CSCO). The computer networking giant, one of the largest Nasdaq components, gapped up nearly 4% after it beat second-quarter estimates late Wednesday. The S&P 500 climbed 0.3%, while the Dow Jones industrial average rose 0.4%. Volume was tracking sharply lower than at the same time Wednesday.