Why it's happening: Keeping in mind shares of IMAX are still up more than 20% over the past six months, the likely culprit for today's decline was an earlier pullback in the broader U.S. markets, which (mostly) dropped in sync with IMAX's temporary plunge today.
That said, possibly contributing to IMAX's decline are SEC filings this morning revealing two separate insider sales. First, the chief business development officer and chief legal officer, Robert Lister, sold 11,750 shares on July 1, 2015, for nearly $470,000, or more than 47% of his stake. In addition, IMAX CEO Greg Foster sold around 3,753 shares the same day for almost $148,000, albeit good for a much smaller 8.4% slice of his own stake in the company.
But I personally don't read too much into those sales, especially considering IMAX's recent rise and solid quarterly report in late April. Executives routinely part with partial stakes in their companies for many different reasons, not the least of which is to pursue proper portfolio diversification. In the end, routine volatility notwithstanding, I think IMAX's long-term story remains firmly intact.