The Rubicon Project, an Internet advertising technology company, said Monday that it added $13 million in venture equity and debt funding, bringing total financial investment in the company to $33 million.

The Los Angeles company, which specializes in ad network optimization, said the round included an additional $5 million in venture funding from Clearstone Venture Partners, Mayfield Fund and IDG Ventures Asia. Silicon Valley Bank provided $8 million in venture debt.

Rubicon is among several startups competing to help Web publishers better manage the wide array of networks that sell Internet ads. The company moves ads that are not being clicked on by viewers to other Web sites in order to maximize viewership of the ads.

The company has largely focused on optimizing viewership of so-called “guaranteed ad inventory,” which essentially are ads that come with minimum viewership guarantees. Chief Executive Frank Addante said the company now plans to heavily expand into technology that optimizes viewing of Internet ads that come without viewership guarantees, so-called “non-guaranteed inventory.”

In the first quarter, which is typically slow after the holidays, the company said it had 150 percent revenue growth over the fourth quarter of 2008.