The CAPTCHA system on this site has just been upgraded. Automated spam to this site is now just about impossible.

The captcha validation and the image handling is done by computers at Carnegie Mellon University.

Carnegie Mellon coordinates the work various institutions are doing to digitise books previously only published on paper.

Users to this site now help these institutions to PROOFREAD those newly scanned books simply by solving a captcha puzzle. People all over the world spend 150.000 hours per day solving some 60 million captcha puzzles. Some of those hours are now effectively applied to help proofread those newly digitised books.

Further reading: http://recaptcha.net/learnmore.html
What is CAPTCHA: http://en.wikipedia.org/wiki/CAPTCHA