Mark Zuckerberg is getting squeezed.

The tech whiz’s Facebook yesterday reported that second-quarter profit margins fell 10 percentage points from last year and that the growth rate of the nearly 1 billion member social network juggernaut slowed considerably.

The late afternoon news shocked investors — and sent Facebook shares tumbling more than 12 percent in after hours trading to a new low of $23.75.

The Menlo Park, Calif., company already saw its value fall by 8.5 percent during regular trading — and is now down 37 percent from its May 17 initial public offering.

Investors were also spooked after Zuckerberg gave no guidance as to how the rest of the year is shaping up.

“A little bit of earnings guidance, a little bit of optimism about future performance would have been nice,” Jordan Rohan, an analyst at Stifel Nicolaus & Co., told Bloomberg.

It was Facebook’s first quarterly report as a public company and Zuckerberg’s first chance to impress public shareholders as a CEO.

The slimmed-down margins — to 43 percent from 53 percent last year — show that Zuckerberg has hit the spending accelerator in hopes of speeding up growth.

So far, it’s not working.

Second-quarter costs and expenses nearly quadrupled to $1.93 billion, thanks to the social network’s share-based compensation expenses.

Capital expenditures grew 213 percent year-over-year, to $413 million, and will rise to between $1.6 billion to $1.8 billion for the year.

The firm recorded a net loss for the quarter of $157 million versus net income of $240 million a year ago. Revenue was $1.18 billion, just a smidgen above the $1.15 billion forecast. Earnings per share were in line at 12 cents.

Zuckerberg, who spoke on the earnings call with COO Sheryl Sandberg and CFO David Ebersman, said the company is set to spend “aggressively” in R&D and chase all the top engineers to add to its almost 4,000-strong staff — still puny by Silicon Valley standards.

Facebook just raided Apple to help develop new generation mobile apps.

Facebook ad revenue grew 28 percent to $992 million.

MediaCom Interaction Managing Director Sloan Broderick, who is working with Facebook on its automated ad product, said that with a huge social event like the Olympics around the corner, both the Street and Madison Avenue might have expected a bigger rise.

“It should have been bigger,” Broderick told The Post. “It is the largest aggregator of consumers and as a platform there has got to be much more we can do with it.”

Execs were light on info about mobile ad spending.

Broderick, though, was optimistic.

“They’re doing all the right things for automation and you’ll see that impact their third and fourth quarter — but we definitely need to hear more about mobile,” he said. “Their scale on mobile is huge and growing, but their ability to develop brand marketing hasn’t been rolled out yet.”