Five percent of Internet users have visited sites accelerated by the Boston-based website optimizier Yottaa, according to the company. That’s a big stat, and investors seem to agree. The company today announced that it had raised $9 million in Series B funding to further develop its web optimization services.

The round included the company’s A round backers, General Catalyst Partners, Stata Venture Partners and Cambridge West Ventures, as well as additional undisclosed investors.

“There is a multi-billion dollar market opportunity that lies ahead for us,” said Yottaa CEO Coach Wei. “In the few months since we launched the Yottaa Site Speed Optimizer service, we have seen tremendous growth and are quickly proving to be the must-have service for mobile and web acceleration.”

The company’s website optimizer currently serves 100 million unique visitors a month, and its mobile acceleration offering has reached more than 30 million users.

Yottaa’s $4 million A round came in August 2010. We took a look at the company’s core product last year, as well as its content delivery network launch earlier this year.