Yahoo Inc. is closing down for a week over the holidays to save money, but experts said the shutdown is par for the course in Silicon Valley. The Internet company is mandating that most of its employees worldwide, except for those responsible for “essential functions” such as customer service, take off work from Dec. 25 through Jan. 1. In the U.S., employees can either use vacation time for nonholiday dates or take unpaid leave. Workers outside the country will be paid according to local standards, said spokeswoman Dana Lengkeek. Sunnyvale, Calif.-based Yahoo told its staff about the break in April, and has recommended employees to take the week off in the past, Lengkeek said. “This is nothing new, just formalized a little more,” she said. “It’s fairly standard in the industry, closing down during a traditionally slow week and giving employees time to recharge. A lot of employees tend to take that week off anyway.” In addition to reducing operations, Yahoo will be turning lights and co...