The price movement is based on difference from the previous day's close, not today's open. Those may differ if there was news overnight. In this case, there is

The price movement is based on difference from the previous day's close, not today's open. Those may differ if there was news overnight. In this case, there isn't really a previous day's close, just the price that was set. Google Finance doesn't seem to show previous close, but Yahoo Finance does: http://finance.yahoo.com/q?s=TWTR http://finance.yahoo.com/q?s=TWTR