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What: Shares of Keynote Systems (UNKNOWN:KEYN.DL) have skyrocketed today by as much as 47% after the company said it would be selling itself.

So what: Private equity firm Thoma Bravo will be acquiring Keynote in an all-cash deal that values the company at $395 million. That pegs Keynote's value at $20 per share, representing a 48% premium over the previous day's close. Shares traded as high as $19.87 today.

Now what: CEO Umang Gupta said that taking the company private will give Keynote flexibility and allow it to invest in its mobile business. The board has already unanimously signed off on the deal, but now it's up to shareholders to approve. The company expects the transaction to close before September 30. Numerous shareholder lawsuits have been filed against the company in the wake of the announcement, alleging that the board breached fiduciary duties by not seeking higher offers.

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Fool contributor Evan Niu, CFA, has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. 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.