Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of (NASDAQ:OSTK) were going through the roof today, climbing as much as 36% after thrashing earnings estimates in its first-quarter report.

So what: The online retailer, which has struggled to turn a profit against the likes of, posted net income of $0.32 a share in the quarter, up from $0.12 a year ago, and well ahead of analyst estimates at $0.13. Revenue also flew past expectations of $282.3 million, climbing 19%, to $312 million. Gross margin improved by 80 basis points, to 18.9%, and nearly all the revenue gains came from fulfillment partner relationships and growth in order size. Management did not provide comment in the press release.

Now what: Overstock's CEO Patrick Byrne also returned earlier this week from a two-month medical absence. It's unclear if there was a specific impetus for Overstock's strong performance, but with a such a narrow profit a year ago at $2.7 million, the company has significant operational leverage, meaning that profits were poised to double or triple with revenue growth. Amazon's decision to begin collecting sales tax in certain states may have also given Overstock some extra business. Amazon shares were off 3.6% today after rival EBay provided disappointing guidance in its quarterly report , falling more than 5% as a result.

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