New Years Eve

Trading will stop at 2 PM ET on New Years Eve. There will be no trading on New Years Day and trading will open normally at 6 PM ET on Sunday. Please note: as is common with many major holidays, liquidity may be lower than usual and spreads may fluctuate accordingly.

** PLEASE NOTE** - THE MARKET CAN OPEN HIGHER OR LOWER THAN THE CLOSE, CAUSING A GAP IN THE PRICES. IF YOUR MARGIN PERCENT ON YOUR ACCOUNT IS CLOSE TO A MARGIN CALL, YOU MAY HAVE POSITIONS CLOSED OUT AUTOMATICALLY AT THE OPEN THIS SUNDAY. CLOSING SOME OF YOUR OPEN POSITIONS YOURSELF TO RAISE YOUR MARGIN PERCENT IS AN OPTION YOU MAY WANT TO CONSIDER.

Another common scenario that can happen when the market gaps over the weekend, your stop order (stop loss) becomes a market order when the price reaches it. (A stop loss is a stop order that becomes a market order when the price reaches it.)

For more information on stop orders, please see the section on “Stop Orders” on page 36 and 37 of the following National Futures Association website:
http://www.nfa.futures.org/NFA-investor-information/publication-library/opportunity-and-risk-entire.pdf

“A stop order is an order placed with your broker to buy or sell a particular futures contract if and when the price reaches a specified level.”

“There can be no guarantee, however, that it will be possible under all market conditions to execute the order at the price specified. In an active, volatile market, the market price may be declining (or rising) so rapidly that there is no opportunity to liquidate your position at the stop price you have designated.”

Stop orders are handled in the same manner in the stock market as well:
http://www.sec.gov/answers/stopord.htm
Here is an excerpt form that section:
A stop order is an order to buy or sell a stock once the price of the stock reaches a specified price, known as the stop price. When the specified price is reached, your stop order becomes a market order. A market order is an order to buy or sell a stock at the current market price.