For the first time, there's expected to be more people visiting retailers' web sites through their smartphones than on desktop computers or tablets during the first weekend of the holiday shopping season that begins on Thanksgiving Day. The bumps in traffic and sales come as retailers try to make the mobile shopping experience easier by improving their mobile apps and adding coupons and other deals. Shoppers also have gotten more comfortable browsing retailers' web sites as smartphone screen sizes have gotten bigger, making it easier for them to see photos of the items they want to buy. Adobe, which measures 80 percent of online sales from the top 100 U.S.