If you had gotten used to relatively modest stock market moves this year, this week has delivered quite a jolt. Technology and financial services shares led the major market barometer down. It was their worst day collectively since late July and the fourth down day in a row of triple-digit moves for the Dow, three of them downward dogs. Worries about global growth, geopolitical tension and some soggy economic data set the tone. Why are these big market gyrations back and what do they mean for your money?