Captcha

Captcha is a program that most websites use. It can tell wether you are a human or a computer. It stops computers from spamming websites and blogs. The program generates two different words and tells you to  type them out, one word is easy to read by humans and computers and the other is a word from an old book, newspaper or radio show. 200 million Captcha's are solved everyday. Each Captcha takes about 10 seconds, altogether these puzzles consume 150,000 hours of our time.