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

Today was a tale of two markets, as investors celebrated the Twitter IPO by pushing the stock up almost 75% from its $26 per share offering price, but the broader stock market dropped substantially. Yet, even though the Dow dropped 1%, and the Nasdaq declined almost 2% on the day, Geron (NASDAQ:GERN), St. Joe (NYSE:JOE), and Tempur-Sealy (NYSE:TPX) all followed Twitter's lead, and posted large gains. Let's take a closer look to find out what sent those stocks soaring today.

Geron vaulted higher by 49% on news that its imetelstat treatment for the bone-marrow disease myelofibrosis had positive results in producing improvement or remission in an early stage study. Yet, shares pulled back after having more than doubled earlier in the day, as analysts weighed the true impact of the finding. Although the results likely justify advancing imetelstat to mid-stage clinical trials, the drug has a long way to go before it can demonstrate broader-based efficacy for larger patient groups.

Land development company St. Joe rose 17% after announcing a deal to sell off a substantial portion of its land assets. The company plans to sell almost 600 square miles of timberland and rural land in northwestern Florida to AgReserves for $565 million. St. Joe CEO Park Brady said that the company should now be able to "concentrate on its core business activity of real estate development in Northwest Florida," and the cash infusion should allow it to take steps to boost shareholder value. With St. Joe also having reported a modest profit for the quarter, the sale demonstrates St. Joe's ability to slim down and make its bigger push toward realizing its best development prospects.

Mattress-maker Tempur Sealy gained 12% after a favorable earnings report last night. The company reversed a year-ago loss, beating adjusted earnings expectations, and more than doubling its revenue after the successful merger of Tempur-Pedic and Sealy. Seeing favorable guidance for the remainder of the year, as well, Tempur Sealy investors now hope that the merger will bring about its anticipated long-term benefits by giving the company offerings at both high-end and low-end price points.

Fool contributor Dan Caplinger has no position in any stocks mentioned. You can follow him on Twitter @DanCaplinger. The Motley Fool owns shares of Tempur Sealy International. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.