CAPTCHA is an acronym for “Completely Automated Public Turing test to tell Computers and Human Apart”. In a broader sense, CAPTCHA is defined as:
Type of challenge-response test used in computing to ensure that the response is not generated by a computer. The process involves one computer (a server) asking a user to complete a simple test which the computer is able to generate and grade…
[“simple” is the key word here]
CAPTCHAs present a very controversial topic: you can’t do without them as a webmaster and you can’t stand them as a user.
Some CAPTCHAs are just impossible to figure – no matter who you are (a robot or a human), you won’t pass the test. Here’s my gallery of impossible CAPTCHAs:
Read fast:
Source: mgccl.com
Find cats:
Source: Depressed Programmer
Train your imagination:
Source: Digg.com
Learn other languages:
Source: Sveit.com
Look for the hidden code:
Source: hidden-3d.com
Just guess:
(The second character cannot be figured I guess)
Source: neogaf.com
(Do you see text at all?)
Source: flickr.com
Know your 1-2-3:
Source: backreaction.blogspot.com
Post image: Geek and Poke via Search Engine People
