Twitter employee Amber Costa works on a computer at Twitter headquarters in San Francisco, California October 4, 2013. Twitter Inc, racing toward the largest Silicon Valley IPO since Facebook Inc's 2012 coming-out party, hopes to woo investors with rip-roaring revenue growth despite having posted big losses over the past three years. The eight-year-old online messaging service gave potential investors their first glance at its financials on Thursday when it publicly filed its IPO documents, setting the stage for one of the most-anticipated debuts in over a year. REUTERS/Robert Galbraith (UNITED STATES - Tags: SCIENCE TECHNOLOGY BUSINESS)