The safety of the Internet is of paramount importance to Google, and helping web developers build secure, reliable web applications is an important part of the equation. To advance this goal, we have released projects such as ratproxy, a passive security assessment tool; and Browser Security Handbook, a comprehensive guide for web developers. We also worked with the community to improve the security of third-party browsers.

http://googleonlinesecurity.blogspot.com/2010/03/meet-skipfish-our-automated-web.html