Facebook's stock fell $3.07 to end the day at $28.84. That's first time it's fallen below $30 since the stock went public.
That price is also 24 percent below its opening price of $38.
The Wall Street Journal that the drop had to do with negative sentiment about the stock, as well as the fact that today traders were able to trade on derivatives.
The Facebook stock saw so much trading, the Journal reports, that it triggered Nasdaq's short sale circuit-breaker.
The paper reports:
"At 2:16 p.m. Eastern Time, the operator of the Nasdaq Stock Market – which hosts Facebook's stock listing – alerted traders that Facebook shares had hit a short-sale circuit breaker. The SEC rule kicks in when a stock drops more than 10% from the prior day's closing price and remains in effect through the rest of the trading day.
"The rule is intended to prevent short sellers from knocking an already-beaten down stock even lower. It seeks to prevent "potentially manipulative or abusive short selling" and facilitate the ability of bullish investors "to sell first upon such a decline," the rule, known as Regulation SHO, states.
"The same circuit breaker was triggered when the stock debuted on May 18."