SF Gate: Yahoo has been working hard to revamp its image among consumers as a company that creates cool apps and content for smartphones. Now, drivers on I-80 in San Francisco will see a large purple sign with the word “Yahoo!” lit up, with different electronic messages displayed. During the weekend, the message read: “It’s good to be back.” The company said it plans to place “topical messages” on the billboard promoting Yahoo properties, products and local events.