NEED fast typer good payout
What is Captcha?
A CAPTCHA is a program that can generate and grade tests that humans
can pass but current computer programs cannot. For example, humans can
read distorted text as the one shown below, but current computer
programs can't:
A CAPTCHA is a program that can
tell whether its user is a human or a computer. You've probably seen
them — colorful images with distorted text at the bottom of Web
registration forms. CAPTCHAs are used by many websites to prevent abuse
from "bots," or automated programs usually written to generate spam. No
computer program can read distorted text as well as humans can, so bots
cannot navigate sites protected by CAPTCHAs.
About 200 million CAPTCHAs are solved by humans around the world
every day. In each case, roughly ten seconds of human time are being
spent. Individually, that's not a lot of time, but in aggregate these
little puzzles consume more than 150,000 hours of work each day. What if
we could make positive use of this human effort? reCAPTCHA does exactly
that by channeling the effort spent solving CAPTCHAs online into
"reading" books.
To archive human knowledge and to make information more accessible to
the world, multiple projects are currently digitizing physical books
that were written before the computer age. The book pages are being
photographically scanned, and then transformed into text using "Optical
Character Recognition" (OCR). The transformation into text is useful
because scanning a book produces images, which are difficult to store on
small devices, expensive to download, and cannot be searched. The
problem is that OCR is not perfect.
reCAPTCHA improves the process of digitizing
books by sending words that cannot be read by computers to the Web in
the form of CAPTCHAs for humans to decipher. More specifically, each
word that cannot be read correctly by OCR is placed on an image and used
as a CAPTCHA. This is possible because most OCR programs alert you when
a word cannot be read correctly.
But if a computer can't read such a CAPTCHA, how does the system know
the correct answer to the puzzle? Here's how: Each new word that cannot
be read correctly by OCR is given to a user in conjunction with another
word for which the answer is already known. The user is then asked to
read both words. If they solve the one for which the answer is known,
the system assumes their answer is correct for the new one. The system
then gives the new image to a number of other people to determine, with
higher confidence, whether the original answer was correct.
(Source -- google recaptcha)
Watch this Captcha entry's Demo work