The 3rd Friday of EVERY MONTH has an important options expiration where investors and traders hedge their risk or speculate on the future direction of the market and then settle out their trades on this particular day.
The end result of all of the buying and selling is an important price, which the market "remembers" as important and usually reacts to it upon returning back to from higher or from lower prices.
Note all of the purple-circled areas to see how the market acts around these key days, which are hidden from view in the way most people look at the market.
If 184 breaks, watch out below.
Tim 7:48PM EST, March 13, 2014