Avvo, the free legal ratings and review site that has taken on the giant legal publishers that have long dominated the business, announced that it has raised $10 million in Series C funding. The new round adds to $13 million previously raised. The round was led by DAG Ventures, which joins existing investors Benchmark Capital and Ignition Partners.

The company’s business model relies on advertising and enhanced legal profiles. Avvo says it now covers 90 percent of U.S. lawyers. Legal is a $225 billion industry in the U.S. The industry spends about $4.5 billion annually on marketing.

CEO Mark Britton says that the company has grown rapidly, and now has 38 employees, including 18 sales people. The key to winning the new funding was the company’s success  in selling advertising to lawyers. Advertising  launched in early 2009, with a wide range of offerings “from $25 to thousands of dollars” a month .

Lawyers are always very busy, but can be sold if you understand their specific needs as a divorce specialist, or a real estate lawyer, says Britton. They also want to do more than by advertising, wanting to discuss ways to improve their profile on the site, etc.  “Lawyers need a lot of help.”