Stocks struggled in afternoon trade Friday, unable to erase much of the morning’s losses. The Nasdaq and the S&P 500 dropped 0.5% each, while the Dow Jones industrial average stumbled 0.8%. Volume was down 10% to 14% on the major exchanges. Amazon.com (AMZN) was adding drag to both major indexes. The stock gapped down 10% after the online merchant missed the Street’s earnings target by 80%.