Fortune: Twitter wants to make it simpler for digital advertisers to get personal with potential customers. What’s more, it doesn’t care much whether prospects are using a web browser or a mobile device to research a purchase. Or both. The social network plans to pay an undisclosed sum for TellApart, a six-year-old marketing software company that drives “hundreds of millions in annual revenue” for retailers like Neiman Marcus, Brookstone, Pottery Barn, and eBags. If all goes as plans, the deal should close by June 1.