Compete, the Boston-based web analytics company, has become the third large Internet company to settle abuse of privacy charges with the U.S. Federal Trade Commission.

Relying upon tracking software that watched customer browsing behavior, private Compete collected data on millions of computer users without disclosing it, then sold data to clients seeking to improve online advertising, the FTC charged.

Compete agreed to a preliminary consent decree to stop the practice, advise clients and agree to audits every two years for the next 20 years. Previously, both Google (Nasdaq: GOOG), the No. 1 search engine, and Facebook (Nasdaq: FB), the No. 1 social networking site, have agreed to similar consent decrees.

The FTC said four commissioner voted to accept Compete’s settlement while one abstained. Public comment on the settlement will be open for 30 days.