If you don't know what a "stack overflow" is, then chances are you don't find yourself trawling the web for answers to obscure computer programming questions. If you did, chances are very high you would end up on Stack Overflow, a question and answer site founded by software expert Joel Spolsky. What began in 2008 as a relatively niche property has grown into one of the 50 biggest websites in the world, covering topics from coding to cooking to golf and averaging 85 million monthly visitors across of network of six sites called Stack Exchange.

Today Stack Exchange announced a $40 million funding round led by Andreessen Horowitz. The money will principally be used to build out Stack Overflow Careers, a site connecting job seekers and companies that are hiring developers. The site gets about 7500 questions a day, about 75 percent of which get answered. Unlike many Q&A sites, such as Quora and Ask.com, Stack Exchange only allows questions with an objective response. You won't find "How can my teenager make friends?" or "What's more disgusting: the men or women's restroom?" Questions that inspire lengthy debate or personal opinion are closed by administrators.

A career site is a natural extension of the Q&A site, because many recruiters already use answers and reputation on the site as a way to evaluate candidates' programming prowess. "A traditional resume will say where someone worked and maybe what team they were on, but it doesn't tell you if they were the best or worst coder there," says Spolsky. "With Stack Overflow Careers, companies can get a good sense of how a programmer thinks, what they know and what they don't."